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UPMSP Vocational Mobile Repairing study materials
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UPMSP Vocational Mobile Repairing practice questions

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Question 1Basic Electronics and Electrical Fundamentals

A mobile phone charger output is marked 5 V / 2 A. What is the maximum power it can deliver?

  1. 7 W
  2. 10 W Correct answer.
  3. 0.4 W
  4. 2.5 W

Explanation

Electrical power in a DC circuit equals voltage multiplied by current, so 5 V times 2 A gives 10 W. The marking states the rated maximum, so the charger can supply up to this value. Multiplying instead of dividing is essential; dividing gives the wrong 0.4 figure.

Question 2Basic Electronics and Electrical Fundamentals

In a mobile handset circuit, which component is used mainly to store charge and block DC while passing AC signals?

  1. Resistor
  2. Inductor
  3. Diode
  4. Capacitor Correct answer.

Explanation

A capacitor stores energy in an electric field between two plates and blocks steady direct current while allowing alternating signals to pass. This makes it common for coupling and decoupling inside phone circuits. Resistors limit current, inductors store energy in a magnetic field, and diodes conduct in one direction.

Question 3Basic Electronics and Electrical Fundamentals

Which material is the best conductor for the internal wiring and PCB tracks of a mobile phone?

  1. Silicon
  2. Copper Correct answer.
  3. Rubber
  4. Mica

Explanation

Copper has very low resistivity and is ductile, so it is used for PCB tracks, wires and connectors. Silicon is a semiconductor, rubber is an insulator, and mica is a dielectric. Low resistivity means charge carriers move easily under an applied voltage.

Question 4Basic Electronics and Electrical Fundamentals

What is the standard nominal voltage of a single lithium-ion cell used in mobile phones?

  1. 9.0 V
  2. 1.5 V
  3. 5.0 V
  4. 3.7 V Correct answer.

Explanation

A single lithium-ion cell has a nominal voltage of about 3.7 V, ranging roughly from 4.2 V fully charged to 3.0 V discharged. The 5 V and 9 V values are charger or USB supply levels, not cell voltage. The 1.5 V value belongs to alkaline dry cells.

Question 5Basic Electronics and Electrical Fundamentals

Which instrument is connected in series with a circuit to measure current?

  1. Ammeter Correct answer.
  2. Ohmmeter
  3. Voltmeter
  4. Oscilloscope probe

Explanation

An ammeter must carry the circuit current, so it is connected in series and has very low internal resistance to avoid disturbing the circuit. A voltmeter is connected in parallel across two points. An ohmmeter works on an unpowered component, and an oscilloscope probe senses voltage.

Question 6Basic Electronics and Electrical Fundamentals

Which colour band commonly represents the digit 2 on a four-band resistor?

  1. Orange
  2. Brown
  3. Red Correct answer.
  4. Yellow

Explanation

In the resistor colour code, red represents the digit 2. Brown is 1, orange is 3, and yellow is 4. Reading the first two bands gives the significant digits, so red in the first position sets a value in the twenties.

Question 7Basic Electronics and Electrical Fundamentals

A wire carries 0.5 A when 6 V is applied across it. What is its resistance?

  1. 3 ohm
  2. 6.5 ohm
  3. 0.083 ohm
  4. 12 ohm Correct answer.

Explanation

Ohm's law states that resistance equals voltage divided by current, so 6 V divided by 0.5 A equals 12 ohm. Multiplying the two values instead of dividing gives 3, which is the power in watts, not the resistance. The correct operation is division.

Question 8Basic Electronics and Electrical Fundamentals

Which component allows current to flow in only one direction and is used for rectification?

  1. Diode Correct answer.
  2. Capacitor
  3. Fuse
  4. Transformer

Explanation

A diode is a semiconductor junction that conducts when forward biased and blocks current when reverse biased, so it can convert AC to pulsating DC. This one-way behaviour is the basis of rectification in charger circuits. Capacitors, transformers and fuses do not perform this function.

Question 9Basic Electronics and Electrical Fundamentals

Two resistors of 100 ohm and 100 ohm are connected in parallel. What is the equivalent resistance?

  1. 100 ohm
  2. 50 ohm Correct answer.
  3. 25 ohm
  4. 200 ohm

Explanation

For two equal resistors in parallel, the equivalent resistance is half of one value, giving 50 ohm. The general formula is the product divided by the sum, which also yields 50 ohm here. Adding the values would apply only to a series connection.

Question 10Basic Electronics and Electrical Fundamentals

A 1000 microfarad capacitor is marked 16 V. What does the 16 V rating indicate?

  1. The voltage it generates when fully charged
  2. The AC ripple it produces
  3. The maximum DC voltage the capacitor can safely withstand Correct answer.
  4. The minimum voltage needed to charge it

Explanation

The voltage rating of a capacitor is the maximum potential difference it can tolerate without dielectric breakdown. Exceeding it risks leakage, bulging or rupture. A capacitor does not generate voltage itself, and charging begins from any applied potential.

Question 11Basic Electronics and Electrical Fundamentals

In a phone charging circuit, a fuse blows repeatedly after replacement. What is the correct first action?

  1. Bridge the fuse holder with wire
  2. Trace and repair the short circuit causing the excess current Correct answer.
  3. Fit a fuse with a higher current rating
  4. Replace the battery and retry

Explanation

A fuse blows because the current exceeds its rating, usually from a short or faulty component. The fault must be located and repaired before power is restored; otherwise the damage continues. Fitting a larger fuse or bridging the holder removes protection and can cause fire or further damage.

Question 12Basic Electronics and Electrical Fundamentals

Which property of a multimeter makes it suitable for measuring voltage across a component without disturbing the circuit much?

  1. Very high input resistance Correct answer.
  2. Very low input resistance
  3. Zero capacitance
  4. High inductance

Explanation

A voltmeter is placed in parallel, so a high input resistance draws very little current and avoids loading the circuit being measured. A low resistance would divert current and give a false reading. This is why good multimeters specify input resistance in megohms.

Question 13Basic Electronics and Electrical Fundamentals

What is the main function of a step-down transformer in a phone charger?

  1. Store energy for the phone battery
  2. Increase the frequency of the mains supply
  3. Reduce the AC mains voltage to a lower level Correct answer.
  4. Convert AC to DC

Explanation

A transformer transfers energy between windings by magnetic induction, and the turns ratio sets the output voltage. In a charger, the secondary has fewer turns, so the mains voltage is stepped down before rectification. Conversion to DC is done by diodes, not the transformer.

Question 14Basic Electronics and Electrical Fundamentals

A resistor has bands brown, black, red, gold. What is its value and tolerance?

  1. 10 ohm, 5 percent
  2. 1000 ohm, 5 percent Correct answer.
  3. 100 ohm, 10 percent
  4. 1200 ohm, 5 percent

Explanation

Brown is 1 and black is 0, giving 10; red as multiplier means times 100, so the value is 1000 ohm. A gold fourth band indicates plus or minus 5 percent tolerance. Reading the multiplier band as a digit is the common error.

Question 15Basic Electronics and Electrical Fundamentals

Why is a bridge rectifier preferred over a single diode in a charger's DC supply?

  1. It doubles the output voltage automatically
  2. It converts DC back to AC
  3. It produces full-wave rectification with better use of the transformer Correct answer.
  4. It removes the need for a smoothing capacitor

Explanation

A bridge of four diodes rectifies both halves of the AC cycle, giving full-wave output with higher average DC and lower ripple than a half-wave single diode. It does not eliminate ripple completely, so smoothing is still needed. It also does not amplify voltage or invert DC to AC.

Question 16Basic Electronics and Electrical Fundamentals

A phone battery of 3000 mAh capacity draws an average current of 600 mA. Approximately how long will it last?

  1. 5 hours Correct answer.
  2. 18 hours
  3. 0.2 hours
  4. 2 hours

Explanation

Battery life in hours equals capacity in mAh divided by current in mA, so 3000 divided by 600 equals 5 hours. This assumes ideal conditions and a constant current. Multiplying the values instead of dividing is the usual mistake.

Question 17Basic Electronics and Electrical Fundamentals

Which effect explains why a current-carrying conductor heats up in a phone's charging path?

  1. Photoelectric effect
  2. Joule heating from I squared R losses Correct answer.
  3. Piezoelectric effect
  4. Magnetic induction

Explanation

Power dissipated as heat in a conductor equals current squared times resistance, known as Joule heating. Thin tracks or poor contacts with higher resistance generate more heat for the same current. This is why chargers and connectors are rated for current and why loose contacts become warm.

Question 18Basic Electronics and Electrical Fundamentals

A technician measures 0 V across a phone's charging connector but the charger is known good. Which condition best explains this?

  1. The battery is fully charged
  2. The connector is open or the protection fuse is blown Correct answer.
  3. The speaker is faulty
  4. The display backlight has failed

Explanation

If a known-good charger delivers no voltage at the connector, the path is interrupted, typically by a blown fuse, broken track or open connector. A fully charged battery would still show charger voltage when connected. Speaker and backlight faults do not affect charging voltage.

Question 19Basic Electronics and Electrical Fundamentals

What is the purpose of the ground or return connection in a mobile phone circuit?

  1. To store charge for the processor
  2. To filter radio signals only
  3. To increase the supply voltage
  4. To provide a common reference and complete the current path Correct answer.

Explanation

Ground provides the zero-volt reference against which other voltages are measured and completes the return path for current. Without it, the circuit is open and no current flows. It does not raise voltage, store charge, or serve only as a radio filter.

Question 20Basic Electronics and Electrical Fundamentals

A 5 V supply feeds a circuit drawing 1.5 A through a cable with 0.2 ohm total resistance. What is the voltage drop along the cable?

  1. 3 V
  2. 0.3 V Correct answer.
  3. 0.13 V
  4. 7.5 V

Explanation

Voltage drop equals current times resistance, so 1.5 A times 0.2 ohm gives 0.3 V. This drop reduces the voltage reaching the phone and dissipates power as heat in the cable. Multiplying voltage by current would give power, not drop.

Question 21Basic Electronics and Electrical Fundamentals

What is the main reason a lithium-ion battery in a phone requires a dedicated charge control IC?

  1. To convert the battery output to AC
  2. To increase the battery's physical size
  3. To manage constant-current and constant-voltage charging stages safely Correct answer.
  4. To boost the speaker volume

Explanation

Lithium-ion cells must be charged with a controlled profile, typically constant current until a set voltage and then constant voltage, with cut-off when current falls. Overcharging or overheating can cause swelling or fire, so the control IC monitors voltage, current and temperature. The IC does not generate AC or affect audio output.

Question 22Basic Electronics and Electrical Fundamentals

A capacitor and a resistor are connected in series across a DC source. What happens to the current after the capacitor is fully charged?

  1. It reverses direction continuously
  2. It falls to nearly zero Correct answer.
  3. It remains at its initial maximum value
  4. It doubles

Explanation

During charging, current flows as charge builds on the capacitor plates. Once the capacitor voltage equals the source voltage, no further current flows, so the current falls to nearly zero. The rate of this change is set by the time constant, resistance times capacitance.

Question 23Basic Electronics and Electrical Fundamentals

A phone shows charging only when the cable is wiggled. Which fault is most consistent with this symptom?

  1. A corrupted firmware image
  2. A loose or cracked solder joint at the charging connector Correct answer.
  3. A discharged battery
  4. A weak Wi-Fi antenna

Explanation

Intermittent charging that responds to movement points to a mechanical or connection fault, such as a cracked solder joint, worn connector pins or a damaged cable. A discharged battery would not charge at all until power is applied, and firmware or antenna issues do not cause movement-dependent charging.

Question 24Basic Electronics and Electrical Fundamentals

Why is a switching regulator often chosen over a linear regulator inside a phone?

  1. It produces no electromagnetic interference
  2. It works only with AC input
  3. It offers higher efficiency by reducing wasted heat Correct answer.
  4. It requires no inductor or capacitor

Explanation

A switching regulator rapidly switches energy through an inductor, so less power is dissipated as heat and efficiency is higher, which matters for battery life and thermal limits. It does need inductors and capacitors and can generate electromagnetic interference. It also operates from DC input, not only AC.

Question 25Basic Electronics and Electrical Fundamentals

A circuit has two 6 V sources connected in series but with opposing polarity. What is the net voltage across the combination?

  1. 0 V Correct answer.
  2. 12 V
  3. 3 V
  4. 6 V

Explanation

When two equal voltage sources are connected in series with opposing polarity, their voltages cancel. Here 6 V minus 6 V equals 0 V. Series sources add only when their polarities aid each other, which would give 12 V.

Question 26Basic Electronics and Electrical Fundamentals

In a mobile phone power section, which unit is used to express the charge stored by a battery, such as a 3000 mAh pack?

  1. Milliwatt
  2. Milliohm
  3. Milliampere-hour Correct answer.
  4. Millivolt

Explanation

Battery capacity is quoted in milliampere-hour, which combines current and time to describe how much charge the cell can deliver. One milliampere-hour equals the charge moved by 1 mA flowing for one hour. Voltage, resistance and power are separate quantities with their own units.

Question 27Basic Electronics and Electrical Fundamentals

A phone's vibrator motor is rated 3 V and draws 80 mA. What power does it consume while running?

  1. 37.5 W
  2. 0.24 W Correct answer.
  3. 0.0375 W
  4. 240 W

Explanation

Electrical power equals voltage multiplied by current, so 3 V times 0.08 A gives 0.24 W. Converting milliamperes to amperes before multiplying keeps the units consistent. This power figure helps a technician judge whether the motor load is within the driver circuit's rating.

Question 28Basic Electronics and Electrical Fundamentals

A technician tests a silicon diode inside a phone's charging path with a digital multimeter in diode mode. What reading is expected when the diode is forward biased and healthy?

  1. About 5 V
  2. About 0.0 V
  3. About 0.6 to 0.7 V Correct answer.
  4. About 12 V

Explanation

A forward-biased silicon junction drops roughly 0.6 to 0.7 V before it conducts appreciably, and a diode-mode test displays this drop. A near-zero reading suggests a shorted junction, while an open or reversed diode shows an overload indication instead of a normal drop. This test quickly confirms whether the diode still rectifies correctly.

Question 29Basic Electronics and Electrical Fundamentals

A coil of wire is used as an inductor in a phone's power circuit. How does an inductor behave immediately after the supply is switched on?

  1. It opposes the rise in current, so current climbs gradually Correct answer.
  2. It blocks current permanently until the supply is removed
  3. It passes full current instantly with no delay
  4. It converts the current directly into a steady voltage

Explanation

An inductor develops a back EMF whenever its current changes, and this opposes the sudden rise of current at switch-on. As a result the current increases along a curve rather than jumping to its final value. Once the current becomes steady, the inductor behaves like a plain length of wire with low resistance.

Question 30Basic Electronics and Electrical Fundamentals

A technician measures 4.2 V at the battery terminals of a phone that will not power on, and the same 4.2 V appears at the input of the main power management IC, but the IC's regulated 1.8 V rail reads 0 V. Which conclusion is best supported by these measurements?

  1. The charging port is open circuit and blocks all current
  2. The battery supply reaches the IC, so the fault lies in the IC or its output path Correct answer.
  3. The 1.8 V rail is normal because the battery voltage is present
  4. The battery is completely discharged and must be replaced

Explanation

The measurements show that the battery voltage is present and reaches the power management IC, so the supply upstream is intact. The missing 1.8 V output points to a fault inside the IC, its enable signal, or the output track and load it feeds. Isolating the output path from the IC confirms which of these is responsible before any part is replaced.

Question 31Mobile Phone Hardware Components and Architecture

In a smartphone block diagram, which component converts the battery's DC voltage into the multiple regulated lower voltages required by the processor and other ICs?

  1. Charging port connector
  2. Audio codec
  3. Antenna switch module
  4. Power management IC (PMIC) Correct answer.

Explanation

The PMIC contains switching and linear regulators (buck and LDO) that step the battery voltage down to the several rails the SoC, memory, and peripherals need, and it also sequences those rails at power-on. Connectors, codecs, and antenna switches do not generate regulated supply rails.

Question 32Mobile Phone Hardware Components and Architecture

A phone shows no charging indication and does not draw current when a known-good charger is connected, but the battery voltage measured at the battery connector is normal. Which component should be checked first in the charging path?

  1. The display flex cable
  2. The charging port and its flex connector Correct answer.
  3. The proximity sensor
  4. The speaker amplifier

Explanation

If the battery itself is healthy but no current enters the phone, the fault lies between the charger and the battery, so the port, its flex, and the protection components near it are the first suspects. Display, audio, and sensor circuits do not sit in the charging current path.

Question 33Mobile Phone Hardware Components and Architecture

Which memory type normally holds the operating system and user data permanently in a smartphone, retaining its contents when power is removed?

  1. EEPROM in the camera module
  2. eMMC or UFS flash storage Correct answer.
  3. LPDDR SDRAM
  4. SRAM cache inside the SoC

Explanation

eMMC and UFS are non-volatile NAND-based flash devices used for the operating system and user files, so data survives a power cycle. DRAM, SRAM, and most working caches are volatile and lose their contents when power is removed.

Question 34Mobile Phone Hardware Components and Architecture

A technician measures about 4.2 V at the battery terminals of a phone that will not power on. What is the most reasonable next step in the power-on troubleshooting sequence?

  1. Check for the presence of the PMIC output rails and the power-on key signal Correct answer.
  2. Replace the display immediately
  3. Reflash the firmware without any measurement
  4. Replace the antenna to improve signal

Explanation

A healthy battery voltage means the fault is downstream, so the logical step is to verify that the PMIC is producing its output rails and that the power key signal reaches the PMIC. Only after confirming these can firmware or display faults be considered.

Question 35Mobile Phone Hardware Components and Architecture

What is the primary function of the baseband processor in a mobile phone?

  1. Handling cellular protocol processing and modem functions Correct answer.
  2. Driving the LCD backlight
  3. Converting AC mains to DC
  4. Amplifying the loudspeaker audio

Explanation

The baseband processor runs the cellular modem stack, handling modulation, coding, and protocol layers for network communication. Backlight, audio amplification, and mains conversion are handled by entirely different circuits.

Question 36Mobile Phone Hardware Components and Architecture

In an RF front-end, what is the purpose of a duplexer in a phone supporting a frequency-division duplex band?

  1. To store the phone's IMEI number
  2. To convert digital audio into analogue audio
  3. To raise the battery voltage for the display
  4. To allow the transmitter and receiver to share one antenna while isolating them from each other Correct answer.

Explanation

A duplexer uses frequency-selective filtering so the transmit and receive paths of an FDD band can share a single antenna without the strong transmit signal desensitising the receiver. It performs no power conversion, identification, or audio function.

Question 37Mobile Phone Hardware Components and Architecture

Which component in a smartphone detects the phone's orientation so the screen can rotate between portrait and landscape?

  1. The accelerometer Correct answer.
  2. The gyroscope only
  3. The ambient light sensor
  4. The fingerprint sensor

Explanation

The accelerometer measures gravity direction along its axes, which lets the system determine whether the phone is held in portrait or landscape orientation. The other sensors serve different purposes and do not by themselves provide the gravity vector used for rotation.

Question 38Mobile Phone Hardware Components and Architecture

A phone's touchscreen does not respond to touch but the display image is perfect. Which assembly is most likely faulty?

  1. The digitiser layer or its flex connector Correct answer.
  2. The vibration motor
  3. The backlight LED string
  4. The main camera module

Explanation

Touch sensing is performed by the digitiser layer and its controller, which communicate through a flex connector; if the image is fine but touch fails, the digitiser path is the prime suspect. Backlight, camera, and motor faults would produce different symptoms.

Question 39Mobile Phone Hardware Components and Architecture

A phone reports no SIM detected even though the SIM card is known to work in another handset. Which area of the hardware should be examined first?

  1. The SIM socket contacts and the SIM interface lines to the baseband Correct answer.
  2. The rear camera flash LED
  3. The earpiece speaker
  4. The Wi-Fi antenna

Explanation

The SIM is read through the socket contacts and a dedicated interface carrying clock, reset, data, and supply lines to the baseband. A working card that is not detected points to those contacts or lines rather than unrelated subsystems.

Question 40Mobile Phone Hardware Components and Architecture

What is the role of the application processor (AP) in a modern smartphone?

  1. It runs the operating system and user applications and controls most peripherals Correct answer.
  2. It only manages battery charging current
  3. It converts RF signals into audio
  4. It provides the reference clock for the RF oscillator

Explanation

The application processor is the main computing unit that executes the operating system and apps and coordinates peripherals such as display, camera, and storage. Charging control, RF-to-audio conversion, and reference clock generation belong to other blocks.

Question 41Mobile Phone Hardware Components and Architecture

During teardown, a technician must disconnect the battery before separating the display flex. Why is this step critical?

  1. To reset the phone's date and time
  2. To prevent short circuits or back-powering that could damage the PMIC and other ICs Correct answer.
  3. To recalibrate the touchscreen
  4. To erase the user's data automatically

Explanation

With the battery connected, loosened flex connectors can short against nearby metal or feed voltage into unpowered circuits, damaging the PMIC and other ICs. Disconnecting the battery removes that risk and is standard practice before handling flex cables.

Question 42Mobile Phone Hardware Components and Architecture

A phone heats up strongly and drains the battery quickly while idle, and the area near the charging IC is warm. Which fault is most consistent with these symptoms?

  1. A scratched display glass
  2. A short or excessive leakage in the charging or power rail circuit Correct answer.
  3. A weak Wi-Fi antenna
  4. A worn loudspeaker

Explanation

Localised heating near the charging IC together with idle current drain indicates abnormal current flow, typically a short or leakage on a power rail. Antenna, glass, and speaker faults do not cause idle current consumption of that kind.

Question 43Mobile Phone Hardware Components and Architecture

Which statement correctly describes the difference between the front camera and the rear camera in most smartphones?

  1. The front camera faces the user for selfies and video calls, while the rear camera faces away for general photography Correct answer.
  2. The front camera connects directly to the baseband modem
  3. The front camera has no image sensor and relies on the display
  4. The rear camera is used only for face unlock and never for photographs

Explanation

The front camera is mounted on the same face as the display so the user can see themselves, and the rear camera points away from the user for normal photography. Both use image sensors and connect to the application processor through camera interfaces.

Question 44Mobile Phone Hardware Components and Architecture

A phone's loudspeaker is silent during calls on speakerphone but the earpiece works normally. What is the most likely fault location?

  1. The gyroscope
  2. The microphone
  3. The SIM reader
  4. The loudspeaker itself or its contact pads and amplifier path Correct answer.

Explanation

Since the earpiece produces sound, the audio codec and call path are largely functional; the fault is confined to the loudspeaker, its spring contacts, or its dedicated amplifier path. Microphone, SIM, and gyroscope faults would give different symptoms.

Question 45Mobile Phone Hardware Components and Architecture

What does the IMEI number of a mobile phone identify?

  1. The Wi-Fi MAC address of the phone
  2. The model of the battery installed
  3. The version of the operating system
  4. The individual handset's identity on cellular networks Correct answer.

Explanation

The IMEI is a unique identifier programmed into the handset that networks use to identify the device and that supports blocking of stolen phones. It is not a battery model, MAC address, or software version indicator.

Question 46Mobile Phone Hardware Components and Architecture

In a phone that supports fast charging over USB, which negotiation typically occurs before the charger raises its output voltage?

  1. The battery is fully discharged first
  2. The phone sends an SMS to the network operator
  3. The charger reads the phone's IMEI from the SIM
  4. The phone and charger exchange a charging protocol handshake over the data lines Correct answer.

Explanation

Fast charging requires the phone and charger to agree on voltage and current using a protocol carried over the data or configuration channel lines. Only after this handshake does the charger raise its output above the standard level.

Question 47Mobile Phone Hardware Components and Architecture

Which architecture is most common in current smartphones, where the modem and application processing are integrated into a single chip?

  1. A purely analogue radio board with no processor
  2. A single-board computer with plug-in modem card
  3. System on chip (SoC) with integrated modem Correct answer.
  4. Separate discrete transistor logic on the mainboard

Explanation

Modern smartphones use an SoC that integrates the application processor, graphics, and often the cellular modem onto one die or package, reducing size and power. Discrete logic, plug-in modem cards, and analogue-only boards do not describe current handset design.

Question 48Mobile Phone Hardware Components and Architecture

A phone's screen shows a completely black image, but when a torch is shone on it a faint image of the home screen is visible. Which circuit is most likely faulty?

  1. The main camera
  2. The charging port
  3. The backlight driver or the backlight LED string Correct answer.
  4. The touch controller

Explanation

A faint but present image means the display panel and its driver are working and only the illumination is missing, which points to the backlight driver or LED string. Touch, camera, and charging faults would not produce this symptom.

Question 49Mobile Phone Hardware Components and Architecture

Which component protects the phone's internal circuitry by clamping excessive voltage transients arriving from the charging port?

  1. TVS diode near the charging connector Correct answer.
  2. Pull-up resistor on the data line
  3. Decoupling capacitor on the speaker output
  4. Ferrite bead on the audio line

Explanation

Transient voltage suppressor diodes are placed near the charging connector to clamp electrostatic discharge and voltage spikes before they reach sensitive ICs. Pull-up resistors, ferrite beads, and audio decoupling capacitors serve signal and filtering roles, not transient clamping.

Question 50Mobile Phone Hardware Components and Architecture

A technician finds that a phone works normally except that it cannot connect to any Wi-Fi network, while Bluetooth works. Which approach best isolates the fault?

  1. Replace the battery immediately
  2. Reflash the bootloader only
  3. Replace the SIM tray
  4. Check the Wi-Fi antenna and its coaxial connector and the Wi-Fi section of the combo chip Correct answer.

Explanation

Wi-Fi and Bluetooth often share a combo chip but use separate antennas and front-end paths, so a Wi-Fi-only failure points to the Wi-Fi antenna, its connector, or the Wi-Fi portion of the chip. Battery, SIM, and bootloader actions do not address that specific path.