HSC Electrotechnology (VET) flashcards
HSC Electrotechnology (VET) · 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
- The relationship V = I × R, where voltage in volts equals current in amperes multiplied by resistance in ohms.
- Electrical power formula
- Power in watts equals voltage multiplied by current (P = V × I); it also equals current squared times resistance (P = I²R).
- Series circuit
- A circuit with one path for current; the current is the same through every component and the total resistance is the sum of the resistances.
- Parallel circuit
- A circuit with more than one current path; the voltage is the same across each branch and the total current is the sum of branch currents.
- Kirchhoff's current law
- The algebraic sum of currents entering and leaving a node is zero; current into a junction equals current out of it.
- RMS value
- The effective value of an alternating quantity; for a sine wave it equals the peak value divided by the square root of two.
- Power factor
- The ratio of true power in watts to apparent power in volt-amperes; it equals the cosine of the phase angle between voltage and current.
- Conductor resistance formula
- Resistance equals resistivity times length divided by cross-sectional area (R = ρL/A); longer or thinner conductors have higher resistance.
- Isolation procedure
- The safe sequence of identifying the circuit, isolating the supply, locking and tagging, proving the tester, testing for dead and re-proving the tester.
- Residual current device
- A protective device that detects imbalance between active and neutral currents caused by earth leakage and disconnects the circuit.
- Hierarchy of control
- The ranked order of risk controls: elimination, substitution, engineering controls, administrative controls and personal protective equipment.
- Voltage drop formula
- For a single-phase two-wire circuit, voltage drop equals two times length times current times resistivity divided by conductor area.
- Cable current-carrying capacity
- The maximum current a cable can carry continuously without exceeding its insulation temperature rating, reduced by derating factors.
- Earth fault-loop impedance
- The total resistance of the path from the live conductor through the fault to earth and back to the supply, which determines fault current.
- MEN system
- The multiple earthed neutral arrangement in which the neutral bar is linked to the earth bar at the main switchboard only.
- Transformer turns ratio
- The secondary voltage divided by the primary voltage equals the secondary turns divided by the primary turns.
- Three-phase power formula
- For a balanced three-phase load, power equals the square root of three times line voltage times line current times power factor.
- Star connection
- A three-phase connection where the phase voltage is the line voltage divided by the square root of three and phase current equals line current.
- Contactor
- A remotely operated electromagnetic switch used to control a load circuit; its coil is controlled by pushbuttons, sensors or a programmable controller.
- Overload relay
- A protective device that trips when sustained current exceeds a set value, protecting a motor from overheating; it does not clear short circuits.
- Diode
- A semiconductor device that conducts current in one direction when forward biased and blocks current when reverse biased.
- Capacitive reactance
- The opposition a capacitor presents to alternating current, equal to one divided by two pi times frequency times capacitance.
- RC time constant
- The product of resistance and capacitance; it is the time for a capacitor to charge to about 63 percent of the supply voltage.
- Programmable logic controller
- An industrial computer that reads inputs, executes a stored program and drives outputs to control machines and processes.
- Ladder diagram
- A control circuit drawing with rails representing supply and rungs containing contacts and coils, read left to right and top to bottom.
- Emergency stop circuit
- A hard-wired, fail-safe control that removes power from controlled equipment when actuated and requires deliberate reset before restart.
- Insulation resistance test
- A test applying a direct voltage, commonly 500 volts, between conductors and earth to confirm insulation is at least one megohm.
- Proving a tester
- Checking a voltage tester on a known live source before and after testing for dead, to confirm it is functioning correctly.
- Personal protective equipment
- Equipment worn by a worker to reduce exposure to hazards, such as insulated gloves, face shields, arc-rated clothing and safety footwear.
- Safe work method statement
- A document that sets out the steps of high-risk work, the hazards of each step and the controls that will be applied.
- Confined space
- An enclosed or partially enclosed space not designed for continuous occupancy, where entry requires a permit and atmospheric testing.
- Variable-speed drive
- An electronic device that varies the frequency and voltage supplied to an induction motor to control its speed and torque.