Answer ALL questions. Look for any feedback given if you get an answer incorrect. Keep choosing an answer until you get it correct. CORRECT or INCORRECT answers are indicated at the TOP of the page. A score is given at the TOP of the page when the exercise has been completed. © K.Brown (2024)

- Calculate the power dissipated a resistance of 12 ohms connected to a 10v power supply.
- 8.33 watts
- 6.22 watts
- 5.92 watts
- 9.93 watts

- The current in a coil changes from 5 amperes to 2 amperes in 50mS and induces a voltage of 30v into the coil. Calculate the value of the inductance of the coil.
- 0.1H
- 0.5H
- 1.1H
- 3H

- What term is used to describe the ability of a capacitor to store a charge?
- capacitance
- charge
- volume
- capacitive reactance

- Calculate the inductive reactance of a coil with inductance of 0.1H, connected to a 50Hz AC supply.
- 314.2 ohms
- 0.3142 ohms
- 3.142 ohms
- 31.42 ohms

- What is the effect of an inductive load on an AC supply?
- power factor lag
- power factor lead
- power factor unity
- no effect

- A pure inductance with 10 ohms inductive reactance is connected to a 100v 50 Hz AC supply. Calculate the power dissipated in the circuit (ignoring any conductor resistance.)
- 1kW
- 100W
- 0kW
- 1W

- The peak-to-peak voltage of a sinusoidal waveform is?
- 0.5 x peak
- peak
- 2 x peak
- 4 x peak

- Which electronic component has the function of detecting changes in light levels?
- photo transistor
- opto coupler
- fibre optic cable
- thyristor

- A 3-phase 4-wire balanced load is connected to a 3-phase 4-wire supply. Each phase draws 65A from the supply. Calculate the neutral current?
- 0A
- 65A
- 195A
- 6.15A

- What cable type is used for underground power distribution?
- MIMS
- PILCSWA
- LSF
- HOFR

- A transformer has 1000v (V pri) and 200v (V sec). If current (pri) is 5A, calculate the secondary current.
- 5A
- 25A
- 1A
- 10A

- What is the primary function of an isolator?
- to make/break current only
- to make/break voltage and current
- to act an an on-load device
- to act as an off-load device

- Which one of the following is the most common earthing system in the UK?
- TNC-S
- TN-S
- TN-C
- TT

- How is the primary earth connection made on a TT earthing system?
- metallic sheath of the supply cable
- earth rod into the ground
- combined earth/neutral conductor
- utilisation of water and gas pipes

- Under what fault conditions does a RCD operate?
- phase to earth fault
- phase to neutral fault
- open circuit fault in a phase conductor
- open circuit in an earth conductor

- What is the primary function of a fuse?
- to protect circuit conductors from damage
- to protect against electric shock
- to protect appliances connected in the circuit
- to protect against motor start-up currents

- Calculate the synchronous speed of the rotating magnetic field in a 4-pole synchronous motor on 50Hz supply?
- 1500rpm
- 750rpm
- 3000rpm
- 1200rpm

- How are the electrical connections made to the rotor of a 3-phase wound rotor induction motor?
- commutator
- slip rings
- direct connection
- via magnetic connection

- What are the running characteristics of a 3-phase cage-rotor induction motor under constant load?
- it runs above synchronous speed
- it runs at synchronous speed
- it runs at various speeds
- it runs at constant speed

- How can the direction of rotation be changed on a single phase capacitor start induction motor?
- reverse the connections to the start winding
- reverse the supply connections to the motor
- reverse the capacitor connections
- add a capacitor in parallel to the supply

- What type of machine is a capacitor start capacitor run motor?
- 3-phase machine
- synchronous machine
- wound rotor machine
- single phase machine

- By what method are small 3-phase cage rotor induction motors started?
- star/delta starter
- DOL starter
- rotor resistance starter
- autotransformer starter

- Newton is the SI unit for ?
- force
- pressure
- mass
- gravity

- kilogram is the SI unit for ?
- mass
- pressure
- weight
- gravity

- what is the SI unit for 'length' or 'distance'?
- metre
- millimetre
- kilometre
- feet/inches

- Calculate the number of seconds in 12 minutes, 5 seconds.
- 720 seconds
- 725 seconds
- 695 seconds
- 700 seconds

- What is the SI unit of measure for 'potential difference' or 'p.d' ?
- amp
- watt
- weber
- volt

- What is the SI unit of measure for 'electromotive force' or EMF ?
- newton
- watt
- weber
- volt

- What term is used to describe the 'amount of matter contained in a body' ?
- mass
- weight
- force
- compression

- What type of force 'holds matter together' ?
- cohesive force
- compressive force
- centrifugal force
- shearing force

- What type of force 'pushes matter together' ?
- cohesive force
- compressive force
- centrifugal force
- shearing force

- What type of force 'acts away from the centres of two rotating masses' ?
- cohesive force
- compressive force
- centrifugal force
- shearing force

- What type of force 'moves the face of one material over another material' ?
- friction force
- compressive force
- centrifugal force
- shearing force

- What SI unit of measure is used for the 'rate that work is done'?
- joule
- watt
- velocity
- newtons per square metre

- A 30 ohm resistance and a coil with inductance of 40 ohms are connected in series to a 100v 50Hz supply. Calculate the total impedance for the circuit.
- 70 ohms
- 50 ohms
- 10 ohms
- 170 ohms

- A 30 ohm resistance and a coil with inductance of 40 ohms are connected in series to a 100v 50Hz supply. Calculate the total current for the circuit.
- 4 amps
- 2 amps
- 2.4 amps
- 4.8 amps

- A 30 ohm resistance and a coil with inductance of 40 ohms are connected in series to a 100v 50Hz supply. Calculate the power-factor for the circuit.
- 0.64
- 0.60
- 0.68
- 0.66

- A 30 ohm resistance and a coil with inductance of 40 ohms are connected in series to a 100v 50Hz supply. Calculate the 'true power' for the circuit.
- 80w
- 120w
- 100w
- 140w

- A 10 ohm, a 30 ohm and a 12 ohm resistor are connected in series. Calculate the total resistance for the circuit.
- 52 ohms
- 62 ohms
- 50 ohms
- 48 ohms

- A 1 ohm and a 4 ohm resistor are connected in parallel. Calculate the total resistance for the circuit.
- 0.8 ohms
- 0.2 ohms
- 5 ohms
- 1.25 ohms

- A 10 ohm, a 30 ohm and a 12 ohm resistor are connected in series to a 10v d.c supply. Calculate the total current for the circuit.
- 0.19 amps
- 0.72 amps
- 1.5 amps
- 0.42 amps

- A 1 ohm and a 4 ohm resistor are connected in parallel to a 10v d.c supply. Calculate the total current for the circuit.
- 12.5 amps
- 2 amps
- 1.25 amps
- 21.2 amps

- What component can be added to large inductive loads to improve the 'power factor'?
- inductors
- capacitors
- resistors
- reactors

- Current in an inductive AC circuit will......?
- lead the supply voltage
- lag behind the supply voltage
- remain in unity with the supply voltage
- become DC

- An AC voltage has a peak voltage of 325v. Calculate the RMS voltage.
- 229.8v
- 206.9v
- 165.6v
- 189.8v

- An AC voltage has a peak voltage of 325v. Calculate the AVERAGE voltage.
- 229.8v
- 206.9v
- 165.6v
- 189.8v

- A lighting source emits 5000Cd and is 4m above a surface. Calculate the illuminance (lux) directly below the light source.
- 313 lux
- 1250 lux
- 223 lux
- 302 lux

- A lighting source emits 5000Cd and is 4m above a surface. Calculate the illuminance (lux) 3m along the surface from directly below the light source.
- 160 lux
- 180 lux
- 175 lux
- 200 lux