Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Previous Year Questions)>Q 3

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Given that the mobility of electron's in Ge is 0.4 metre square/volt sec and electronic charge is 1.6 x10^–19C . How many donor atom (per m³) have in semiconductor of conductivity 500 mho/m :-

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Important Questions on Current Electricity

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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Analytical Questions)>Q 1

A DC motor operates with

220 V

mains. Initially, it draws a current of

20 A

. The resistance of the starter is

6 Ω

. When the motor runs at its full speed it consumes

500 W

power. Find the current drawn by it.

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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Analytical Questions)>Q 2

The figure shows a circuit that contains three identical resistors with resistance $R = 9.0 Ω$ each, two identical inductors with inductance $L = 2 mH$ each, and an ideal battery with emf $ε = 18 V$ . The current $i$ through the battery just after the switch closed is-
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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Analytical Questions)>Q 3

What will be conductivity of pure silicon crystal at 300 K temperature. If electron hole pairs per cm³ is 1.072 x 10¹⁰ at this temperature,

μ_{e}

= 1350 cm²/volt-s and

μ_{h}

= 480 cm²/volt-s :-

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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Assertion & Reason)>Q 1

If voltage across a bulb rated

220

Volt-

100

Watt drops by

2.5 %

of its rated value, the percentage of the rated value by which the power would decrease is :

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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Assertion & Reason)>Q 2

An electron is moving in a circle of radius 5.1 × 10^–11 m. at a frequency of 6.8 × 10¹⁵revolution/sec. The equivalent current is approximately :-

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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Assertion & Reason)>Q 3

Assertion : In higher power transmission, 240 V is preferred over 120 V.
Reason : Power loss is more in case of 120 V as compared to 240 V.

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Beta Question Bank for Medical: Physics>Chapter 24 - Current Electricity>Exercise (Assertion & Reason)>Q 4

Assertion: The resistance of a coil for direct current is $5 Ω$ . An alternating current is sent through it. The resistance will remain same.

Reason: The resistance of a coil does not depend upon nature of current.