Current electricity

21. Which one of the following does not have negative temperature coefficient?

Aluminium
Paper
Rubber
Mica

Detailed SolutionWhich one of the following does not have negative temperature coefficient?

22. Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes

$$ rac{1}{9}$$ times
3 times
9 times
Unchanged

Detailed SolutionCopper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes

23. Electric pressure is also called

Resistance
Power
Voltage
Energy

Detailed SolutionElectric pressure is also called

24. The filament of an electric bulb is made of

Carbon
Aluminium
Tungsten
Nickel

Detailed SolutionThe filament of an electric bulb is made of

25. Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open

There will be heavy current in the main line
Rest of the two bulbs will not light
All three bulbs will light
The other two bulbs will light

Detailed SolutionThree 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open

26. Which method can be used for absolute measurement of resistances?

Lorentz method
Raleigh method
Ohm's law method
Wheatstone bridge method

Detailed SolutionWhich method can be used for absolute measurement of resistances?

27. Insulating materials have the function of

Preventing a short circuit between conducting wires
Preventing an open circuit between the voltage source and the load
Conducting very large currents
Storing very high currents

Detailed SolutionInsulating materials have the function of

28. Bulbs in street lighting are all connected in

Parallel
Series
Series-parallel
End-to-end

Detailed SolutionBulbs in street lighting are all connected in

29. Voltage dependent resistors are used

For inductive circuits
To suppress surges
As heating elements
As current stabilizers

Detailed SolutionVoltage dependent resistors are used

30. With rise in temperature the resistance of pure metals

Increases
Decreases
First increases and then decreases
Remains constant

Detailed SolutionWith rise in temperature the resistance of pure metals

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