Hi everyone, i see this theme is not used from long time but i want to share my questions with you, i dont have the answers but i hope that will be helpful to someone
1. Calculate the current by a 100 Watt lamp having a working resistance of 200 Ohms
a) 0.637 A
b) 0.707 A
c) 0.881 A
d) 1.414 A
2. The efficiency of an electric motor is given by expression
a) Input/ Output
b) Input+ losses
c) Output+ losses
d) Output/ Input
3. If a cable must carry a current of 19.5 A with a voltage drop of not more than 6 V, its resistance must not exceed
a) 32.5 Ohms
b) 1170 Ohms
c) 0.308 Ohms
d) 3.25 Ohms
4. The voltage applied to a circuit is 230 V, if the circuit current is a 3.8 A calculate the power used
a) 632 W
b) 63.2 W
c) 874 W
d) 0.016 W
5. A faulty cable joint carries a current of 12.5 A, and a voltage drop of 7.5 V appears across the joint. The power wasted
at the joint is:
a) 1.67 W
b) 0.6 W
c) 93.8 W
d) 60 W
6. 45 micro s is equivalent to:
a) 0.45 s
b) 0.045 s
c) 0.0045 s
d) 0.000 045 s
7. A current of 4.5 A flows in a 3.5 Ohm resistor for 5.5 minutes. The energy dissipated is
a) 476 J
b) 390 J
c) 23 389 J
d) 18 191 J
8. The power developod in resistor of 24 Ohm is 225 W. The Current Flowing is:
a) 0.327 A
b) 3.06 A
c) 9.68 A
d) 30.6 A
9. The resistance of a 110 V, 100 W lamp is:
a) 1210 Ohm
b) 0.011 Ohm
c) 8.26 Ohm
d) 121 Ohm
10. A 2.5 kW heater is in use for 7.5 hours daily and energy costs 7.1p per unit. The total cost of running heater over a
month of 28 days is:
a) 372.75 pounds
b) 133.31 pounds
c) 37.28 pounds
d) 1.33 pounds
11. A secondary cell is one which
a) is less efficient than primery cell
b) cannot be recharged when exhausted
c) can be recharged after use by means of a charging current
d) can be used only for stand by purposes
12. The standard form of dry cell or battery is called the:
a) Leclanche type
b) zinc- chloride type
c) lead- acid type
d) lithium type
13. An cinventional current is considered to consist of
a) a drift of electrons from negative to positive
b) a movement of positive ions from positive to negative
c) an electric fluid travelling from positive to negative
d) a drift of electrons from positive to negative
14. The unit of electric current is the:
a) Ampere
b) Watt
c) Joule
d) Cpulomb
15. The element nickel is:
a) a soft metal
b) an electrical conductor
c) a kind of money
d) an electrical insulator
16. The symbol U is used to denote:
a) potential difference
b) a matteria unsuitable for electrical use
c) electrical resistivity
d) a voltmeter
17. The formula which relates resistance, potential difference and current is
a) I=U/R
b) R=IU
c) R=U
d) Rt= Ri+R2
18. Four equal resistors are connected in series and their combined resistance is 18.8 Ohm. The value of each resistor is:
a) 9.4 Ohm
b) 75.2 Ohm
c) 4.7 Ohm
d) 37.6 Ohm
19. To resistors of equal value are connected to three other resistors fo value 33 Ohm, 47 Ohm and 52 Ohm to form a series
group of resistors whit a combined resistance of 160 Ohm. What is the individual resistance of two unknown resistors?
a) 7 Ohm
b) 14 Ohm
c) 28 Ohm
d) 42 Ohm
20. If a current of 26 mA flows in a circuit when a 24 V supply is connected to it, its resistance is
a) 923 Ohm
b) 108 Ohm
c) 9.23 Ohm
d) 9.3 Ohm
21. To read a current correctly, an ammeter must be connected
a) so that no current passes through it
b) directly across the supply
c) in parallel with the ciruit concerned
d) in series with the circuit concerned
22. The combined resistance of 56 Ohm, 12 Ohm and 33 Ohm resistors connected in parallel is
a) 101 Ohm
b) 7.60 Ohm
c) 7.07 Ohm
d) 20.4 Ohm
23. 0.6 MOhm is equivalent to:
a) 6000 Ohm
b) 60 000 Ohm
c) 600 000 Ohm
d) 6000 000 Ohm
24. A space in which magnetic effects can be detected is called
a) permeability
b) a magnetic field
c) magnetic flux
d) lines of force
25. If south- seeking poles of two magnets are brought close together, they will:
a) repel each other
b) be unaffected
c) pull together
d) attract each other
26. A current flowing towards the viewer in a cross- sectioned conductor is shown by:
a) clockwise concentric circles
b) a cross
c) a dot
d) anticlockwise concentric circles
27. The power dissipated in a 800 Ohm resistor connected to a 230V supply is:
a) 66 W
b) 0.3 A
c) 7.2 W
d) 192 W
28. An electric lamp is rated at 60 W. The current it draws from 230 V supply is:
a) 4 A
b) 14.4 m A
c) 6.94
d) 0.26 A
29. If a 60 W lamp is left on for eight hours and electrical energy costs 7p per unit, the cost will be:
a) 3.36p
b) 5.25p
c) 6.86p
d) 3.36 pounds
30. The energy used by a 60 W lamp in eight hours is:
a) 28.8 KJ
b) 1728 KJ
c) 480 KJ
d) 60 W
31. The volt drop in cable carrying a current is due to its
a) impedance
b) resistance
c) size and type
d) reactance
32. The resistance of a conductor is
a) directly proportional to its length
b) independent of its dimensions
c) directly proportional to its cross- sectional area
d) small
33. A conductor has a cross- sectional area of 20 mm2, a lench of 48 m and is made of material with a resistivity of
0.02 micro ohm m. Its resistance is
a) 48 kOhm
b) 28 Ohm
c) 0.48 Ohm
d) 0.048 Ohm
34. If a carbon resistor increases in temperature its resistance will
a) decrease
b) be unchanged
c) increased
d) fall to zero
35. The current to a tungsten- filament lamp at the moment of swich- on
a) will blow the circuit fuse
b) is lower than the steady running current
c) usually causes the filament to burn out
d) is significantly greater than after a second or so
36. The number of cycles of an alternating system traced out each second is called the:
a) periodic time
b) half cycle time
c) waveform
d) frequency
37. The periodic time of an alternating- current system is the
a) time taken for completion of one cycle
b) time before a positive half cycle fall to zero
c) time taken for completion of a half cycle
d) usually about one second
38. The frequency of an alternating electrical system is measured in
a) cycles
b) volts
c) hertz
d) seconds
39. A major advantage of an alternating- current supply system over a direct current system is that
a) electric shocks are likely to be less severe
b) the cost will be lower
c) the current has many values instead
d) transformers will not operate efficiently on direct- current supplies
40. The highest value reached by an alternating voltage in a half cycle is called the
a) maximum or peak value
b) instantaneous value
c) root- mean- squere value
d) average value
41. The RMS (root- mean- squere) value of an alternating current is
a) the peak value of a squere- wave system
b) seldom used because it is so difficult to calculate
c) the effective value which is almost always given
d) the squere root of the average vaue
