# 02 UNIT 7 PHYSICS STUDENT COPY converted watermarked.pdf

## 02 UNIT 7 PHYSICS STUDENT COPY converted watermarked.pdf

TOPICS:

✓ Current Electricity

Q. 1 The specific resistance of managing is 50×10−8ohm m. The resistance of a cube of

length 50cm will be

A. 10−6ohm B. 10−8ohm

C. 2.5×10−5ohm D. 5×10−4ohm

Q. 2 When the length and area of cross-section both are doubled, then its resistance

A. Will become half B. Will remain the same

C. Will be doubled D. Will become four times

Q. 3 The resistance of a wire is 20 ohms. It is stretched so that the length becomes three

times, then the new resistance of the wire will be

A. 6.67 ohms B. 120 ohms

C. 60.0 ohms D. 180.0 ohms

Q. 4 Ohm's law is true

A. For metallic conductors at low temperature

B. For electrolytes when current passes through them

C. For metallic conductors at high temperature

D. For diode when current flows

Q. 5 62.5×1018 electrons per second are flowing through a wire of area of cross-section

0.1m2

, the value of current flowing will be

A. 1 A B. 10 A

C. 0.1 A D. 0.11 A

Q. 6 In a semiconductor, an electric current flow due to

A. Free electrons B. Positive and negative ions

C. Free electrons and holes D. Protons

Q. 7 A certain piece of silver of given mass is to be made like a wire. Which of the following

combination of length (L) and the area of cross-section will lead to the smallest resistance?

A. L and A

B. L/2 and 2 A

C. 2L and A/2

D. Any of the above, because volume of silver remains same

Q. 8 The drift velocity does not depend upon

A. Cross-section of the wire B. Number of free electrons

C. Length of the wire D. Magnitude of the current

Q. 9 A cell of e.m.f.1.5Vhaving a finite internal resistance is connected to a load resistance of

2Ω. For maximum power transfer the internal resistance of the cell should be

A. 4 ohm B. 2 ohm

C. 0.5 ohm D. None of these

Q. 10 A 50V battery is connected across a 10-ohm resistor. The current is 4.5 amperes.

The internal resistance of the battery is

A. Zero B. 1.1-ohm

C. 0.5-ohm D. 5.0 ohm

Q. 11 A 25-watt, 220-volt bulb and a 100-watt, 220-volt bulb are connected in parallel

across a 220-volt line. Which bulb will glow more brightly?

A. 25-watt bulb B. Both will have same brightness

C. 100-watt bulb D. First 25 watt then 100 watts

Q. 12 Which of following is not same as watt?

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