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In the circuit shown below, the key is pressed at time $t = 0 .$ Which of the following statement(s) is (are) true?

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Important Questions on Current Electricity

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 4

Let

C

be the capacitance of a capacitor discharging through a resistor

R

. Suppose

t_{1}

is the time taken for the energy stored in the capacitor to reduce to half its initial value and

t_{2}

is the time taken for the charge to reduce to one-fourth its initial value. Then the ratio

t_{1} / t_{2}

will be

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 5

A resistor

R

and

2 μF

capacitor in series are connected through a switch to

200 V

direct supply. Across the capacitor is a neon bulb that lights up at

120 V

. Calculate the value of

R

to make the bulb light up

5 s

after the switch has been closed.

(\log_{10} 2.5 = 0.4)

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 6

A combination of two identical capacitors, a resistor

R

and a

D C

voltage source of voltage

6 V

is used in an experiment on a

(C - R)

circuit. It is found that for a parallel combination of the capacitor the time in which the voltage of the fully charged combination reduces to half its original voltage is

10 second

. For series combination, the time needed for reducing the voltage of the fully charged series combination by half is

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 7

The figure shows an experimental plot discharging of a capacitor in an $R C$ circuit. The time constant $τ$ of this circuit lies between

Question Image

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 8

Consider two different metallic strips

(1 and 2)

fo the same material. Their lengths are the same, width are

w_{1}

and

w_{2}

and thicknesses are

d_{1}

and

d_{2}

, respectively. Two points

K

and

M

are symmetrically located on the opposite faces parallel to the

x - y

plane (see figure).

V_{1}

and

V_{2}

are the potential differences between

K

and

M

in strips

1

and

2

, respectively. Then, for a given current

I

flowing through them in a given magnetic field strength

B

, the correct statement(s) is (are)

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 12

A superconductor has

T_{C} (0) = 100 K .

When a magnetic field of

7.5

Tesla is applied, its

T_{C}

decreases to

75 K .

For this material, one can definitely say that when:

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 13

By increasing the temperature, the specific resistance of a conductor and semiconductor

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Alpha Question Bank for Engineering: Physics>Chapter 24 - Current Electricity>Exercise - 3>Q 14

A strip of copper and another of germanium are cooled from room temperature to

80 K .

The resistance of

In the circuit shown below, the key is pressed at time t= 0. Which of the following statement(s) is (are) true?

Important Questions on Current Electricity

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In the circuit shown below, the key is pressed at time $t = 0 .$ Which of the following statement(s) is (are) true?