UPMSP High School Electrician flashcards
UPMSP High School Electrician · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Ohm's law
- For a conductor at constant temperature, voltage equals current multiplied by resistance. It relates the three quantities and allows any one to be calculated when the other two are known.
- Series circuit
- A circuit in which components are connected end to end so the same current flows through each. Total resistance is the sum of individual resistances, and supply voltage divides across them.
- Parallel circuit
- A circuit in which components are connected across the same two points so the same voltage appears across each. Total resistance is found from the reciprocal sum, and current divides between branches.
- RMS value
- The effective value of an alternating current or voltage that produces the same heating effect as an equal direct current. For a sine wave it equals peak value divided by the square root of two.
- Two-way switch
- A switch with one common terminal and two changeover terminals. Two such switches, connected by a three-core cable, control one lamp from two different positions such as the ends of a staircase.
- Megger test
- An insulation resistance test performed with a high-voltage DC instrument, usually at 500 V. The circuit must be isolated and de-energised, and the result is read in megohms.
- PVC conduit wiring
- A wiring method in which insulated conductors are drawn through rigid PVC pipes fixed to the surface or concealed in walls. It protects cables from moisture and mechanical damage and is common in damp locations.
- Cable colour code
- The standard identification of conductors by insulation colour. In single-phase Indian practice, phase is red or brown, neutral is black or blue, and earth is green or green-yellow.
- Transformer EMF equation
- The induced EMF in a transformer winding equals 4.44 times frequency times turns times maximum flux. It shows that EMF depends on supply frequency, number of turns, and core flux.
- Slip
- The difference between synchronous speed and actual rotor speed of an induction motor, expressed as a fraction of synchronous speed. Slip increases with load and is zero at no load.
- Star-delta starter
- A starter that connects the motor stator in star during starting and in delta during running. Starting current and torque are reduced to one third of direct-on-line values.
- Back EMF
- The voltage induced in a DC motor armature that opposes the applied voltage. It equals supply voltage minus the armature current multiplied by armature resistance, and it limits armature current.
- Shunt resistor
- A low-value resistor connected in parallel with an ammeter to divert most of the current. It extends the current range of the meter while keeping the meter movement within its rating.
- Clamp meter
- An instrument that measures current by opening a magnetic core around a single conductor. It does not require breaking the circuit and is useful for checking load current in live cables.
- Energy meter constant
- The number of revolutions made by the meter disc for each kilowatt-hour of energy consumed. It is used to calculate energy from the observed revolutions and time.
- Accuracy class
- A number that states the maximum permissible error of an instrument as a percentage of full-scale deflection. A class 1.0 meter may deviate by up to one percent of full scale.
- Diversity factor
- The ratio of the sum of individual maximum demands to the maximum demand of the whole installation. It is applied in load estimation because not all connected loads operate at the same time.
- Lighting sub-circuit
- A final circuit supplying lamps and small lighting points. In domestic installation practice it is commonly limited to about 800 watts or ten points and is protected by a 6 A or 10 A device.
- Distribution board
- An enclosure that receives the main supply and distributes it through protective devices to final circuits. It is installed near the entry point and at a convenient operating height.
- Voltage drop limit
- The maximum permitted loss of voltage along a final circuit, commonly three percent of nominal supply voltage. It is checked after cable size is selected by current-carrying capacity.
- MCB
- A miniature circuit breaker that trips automatically on overload by thermal action and on short circuit by magnetic action. It can be reset after the fault is cleared.
- RCD
- A residual current device that detects imbalance between phase and neutral currents and trips at a set sensitivity, commonly 30 milliamperes. It protects people against earth leakage, not against overload.
- Plate earthing
- An earthing method using a copper or galvanised iron plate buried vertically in the ground with layers of charcoal and salt. It provides a low-resistance path for fault current to earth.
- Lockout and tagout
- A safety procedure in which the supply is isolated, the switch is locked, and a warning tag is attached. The circuit is then proved dead before work begins.
- Nichrome
- A nickel-chromium alloy with high resistivity and good oxidation resistance at high temperature. It is widely used for heating elements in irons, heaters, and ovens.
- Crimping
- A method of joining a conductor to a lug or terminal by mechanically compressing a metal sleeve. A correct die size produces a gas-tight joint with low electrical resistance.
- Luminous efficacy
- The ratio of luminous flux emitted by a lamp to the electrical power it consumes, expressed in lumens per watt. It measures how efficiently a lamp converts electrical energy into light.
- Illuminance
- The amount of light falling on a surface per unit area, measured in lux. One lux equals one lumen per square metre, and recommended values depend on the task performed.
- Induction heating
- A heating method in which alternating current in a coil induces eddy currents in a conducting workpiece. Heat is generated inside the material, giving fast and efficient heating.
- Britannia joint
- A straight joint used on overhead conductors, made by binding the cleaned conductors together with a thinner wire. It is mechanically strong and suitable for exposed outdoor lines.
- Polarity test
- A check that phase, neutral, and earth are connected to the correct terminals of a socket. Viewed from the front, phase is on the right, neutral on the left, and earth at the top.
- Quotation
- A written offer by a supplier or contractor to provide goods or services at a stated price under stated terms. It is not a bill and usually has a validity period.