Current electricity

1. If the efficiency of a machine is to be high, what should be low?

Input power
Losses
True component of power
kWh consumed

Detailed SolutionIf the efficiency of a machine is to be high, what should be low?

2. The weight of an aluminium conductor as compared to a copper conductor of identical cross-section, for the same electrical resistance, is

50%
60%
100%
150%

Detailed SolutionThe weight of an aluminium conductor as compared to a copper conductor of identical cross-section, for the same electrical resistance, is

3. A rheostat differs from potentiometer in the respect that it

Has lower wattage rating
Has higher wattage rating
Has large number of turns
Offers large number of tapping

Detailed SolutionA rheostat differs from potentiometer in the respect that it

4. If a parallel circuit is opened in the main line, the current

Increases in the branch of the lowest resistance
Increases in each branch
Is zero in all branches
Is zero in the highest resistive branch

Detailed SolutionIf a parallel circuit is opened in the main line, the current

5. The substances which have a large number of free electrons and offer a low resistance are called

Insulators
Inductors
Semiconductors
Conductors

Detailed SolutionThe substances which have a large number of free electrons and offer a low resistance are called

6. Three resistances of 10 ohms, 15 ohms and 30 ohms are connected in parallel. The total resistance of the combination is

5 ohms
10 ohms
15 ohms
55 ohms

Detailed SolutionThree resistances of 10 ohms, 15 ohms and 30 ohms are connected in parallel. The total resistance of the combination is

7. An electric filament bulb can be worked from

D.C. supply only
A.
supply only B. A.C. supply only C. Battery supply only
All above

Detailed SolutionAn electric filament bulb can be worked from

8. A resistance having rating 10 ohms, 10 W is likely to be a

Metallic resistor
Carbon resistor
Wire wound resistor
Variable resistor

Detailed SolutionA resistance having rating 10 ohms, 10 W is likely to be a

9. For testing appliances, the wattage of test lamp should be

Very low
Low
High
Any value

Detailed SolutionFor testing appliances, the wattage of test lamp should be

10. When one leg of parallel circuit is opened out the total current will

Reduce
Increase
Decrease
Become zero

Detailed SolutionWhen one leg of parallel circuit is opened out the total current will

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