Applied Electricity

Question 1

1Power factor in an a.c. circuit is

Medium

A. resistance ÷ current B. apparent power ÷ true power C. voltage × current D. true power ÷ apparent power

Question 2

2The three terminals of a bipolar junction transistor are

Easy

A. gate, source and drain B. anode, cathode and gate C. positive, negative and earth D. emitter, base and collector

Question 3

3The output voltage of a generator increases with

Easy

A. faster rotation B. weaker magnets C. slower rotation D. fewer turns

Question 4

4Three 6 Ω resistors are connected in parallel. What is the total resistance?

Easy

A. 3 Ω B. 18 Ω C. 6 Ω D. 2 Ω

Question 5

5A transformer with more secondary turns than primary turns is a

Easy

A. rectifier B. isolating transformer only C. step-up transformer D. step-down transformer

Question 6

6The unit of electric charge is the

Easy

A. volt B. coulomb C. ohm D. ampere

Question 7

7Resistors of 4 Ω and 12 Ω are connected in parallel. Find the equivalent resistance.

Easy

A. 16 Ω B. 3 Ω C. 8 Ω D. 48 Ω

Question 8

8A transistor used as an amplifier

Easy

A. blocks all current B. stores charge C. converts AC to DC D. increases the strength of a signal

Question 9

9A transformer has a primary voltage of 240 V and a secondary voltage of 12 V. If the primary has 2,000 turns, find the secondary turns.

Medium

A. 40,000 B. 1,000 C. 200 D. 100

Question 10

10Find the power used by a device drawing 5 A from a 230 V supply.

Easy

A. 46 W B. 2,300 W C. 1,150 W D. 235 W

Question 11

11Resistors of 3 Ω and 6 Ω in parallel have a combined resistance of

Easy

A. 4.5 Ω B. 18 Ω C. 2 Ω D. 9 Ω

Question 12

12Switches should always be connected in the

Hard

A. earth wire B. live wire C. any wire D. neutral wire

Question 13

13The brown wire in a flexible cord is the

Hard

A. neutral B. live C. switch wire D. earth

Question 14

14A Zener diode is used mainly for

Easy

A. amplification B. light emission C. voltage regulation D. storage

Question 15

15The internal resistance of a cell causes

Medium

A. the e.m.f. to rise B. the terminal voltage to fall when current flows C. no effect D. an infinite current

Question 16

16A diode allows current to flow

Easy

A. in both directions B. only when cold C. never D. in one direction only

Question 17

17Hysteresis loss in a transformer core is reduced by using

Hard

A. solid iron B. aluminium C. silicon steel D. copper

Question 18

18A step-down transformer has

Easy

A. equal turns B. more turns on the secondary C. no primary coil D. fewer turns on the secondary than the primary

Question 19

19In a purely resistive AC circuit, the current and voltage are

Easy

A. in phase B. 90° out of phase C. 45° out of phase D. 180° out of phase

Question 20

20The period of a 50 Hz supply is

Hard

A. 0.02 s B. 0.5 s C. 50 s D. 0.2 s