An inductor of 300mH placed on a 60Hz network will have an inductive reactance of?
113Ω
100Ω
113097Ω
97Ω
A capacitor of 90µF is placed on an electrical network of frequency 65 Hz. What is the value of capacitive reactance?
27Ω
27000000Ω
27000Ω
0.0027Ω
What is the typical generation voltage at a power station?
25kV
125kV
11kV
33kV
Where is the neutral connected on the secondary of a delta to star transformer?
The end of every line
The star point of the transformer
To the middle of every winding
Left floating
What is the phase separation angle in a typical star system between phases?
100°
120°
360°
110°
A voltage of 700V is applied to two resistors in series. A current of 2.8A flows. If one of the resistors is 150Ω what is the value of the other?
50Ω
75Ω
124Ω
What is the series impedance of a circuit where the resistance is 30Ω the inductive reactance is 70Ω and the capacitive reactance is 30Ω?
65Ω
70Ω
40Ω
If you have a star phase voltage of 135V what would the line voltage be?
234V
200V
78V
75V
A 30kW lift motor is running at 0.95 power factor. Calculate the line current that is drawn from the supply when the voltage is 390V:
47A
40A
37A
50A
What type of light fitting requires no control gear?
Incandescent
Fluorescent
Sodium Discharge
High pressure mercury
Which type of protective device natively offers the functions of earth fault, residual current and short circuit protection?
RCBO
MCB
RCD
ACB
A light source of 300 Candela is placed 2.5m above a table. Calculate the illuminance at a point directly below the light fitting.
48 Lux
48 Lumens
120 Lux
120 Lumens
The full load current of a transformer is 650A and the voltage is 400V between phases. Calculate the apparent power rating of the transformer.
450kVA
400kVA
180kVA
400kW
In a TT system the means of earthing is provided by:
Distributor's earth supply
Installation earth electrode
Combined neutral and earth
None it is an earth free location
The phase voltage supplied to a building is 270V. The building is given a 3 phase 3 wire supply. What voltage are available to work with?
270V and 468V
468V
270V, 468V and 135V
300V
300V and 500V
Calculate the angle the current lags the voltage in a network where there is 30kW and 12kVAr on the network.
21.8°
18°
25°
26.7°
A centre tapped to earth transformer has a voltage of 75V phase to earth. What would the full voltage available be?
150V
100V
37.5V
130V
A 25kW load is being drawn from a supply at 350V. Calculate the power loss through the conductor if the resistance is measured at 0.3Ω.
1000W
1640W
1530W
2160W
The potential difference between a cat and the earth is 1000V. If the resistance of the cat is measured at 250Ω what would the current flow to earth be?
10A
250000A
4V
4A