Physics Test 129

Result

Physics Test 129

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Weekly Quiz Competition

Question 1
4 / -1

The varying current in a coil changes from 10 A to zero in 0.5 s. If the average emf induced in th coil is 220 V, then the self-inductance of the coil will be

A
22 H

B
11 H

C
5.5 H

D
None of these
Question 2
4 / -1

Magnetic flux in a circuit containing a coil of resistance 2Ωchanges from 2.0 Wb to 10 Wb in 0.2 s. The charge passed through the coil in this time is

A
0.8 C

B
1.0 C

C
5.0 C

D
4.0 C
Question 3
4 / -1

A metallic square loop ABCD is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in the figure. An electric field is induced

A
in AD, but not in BC

B
in BC, but not in AD

C
neither in AD nor in BC

D
in both AD and BC
Question 4
4 / -1

In the circuit shown in the figure, what is the value of I₁ just after pressing the key K?

A
5/7 A

B
5/11 A

C
1 A

D
None of these
Question 5
4 / -1

A uniform but time-varying magnetic field B(t) exists in a cylindrical region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region

A
is zero P

B
decreases as 1/r

C
increases as r

D
decreases as 1/r²
Question 6
4 / -1

A

B

C

D

Solution

Potential difference between point O & P is V_O – VA.

Potential difference between point O & Q is V_O – VC

Potential difference between point P & Q is

VA – VC = (V_O – VC) – (V_O – VA) (1)

Now for a rotating rod emf = BVℓ

Consider a small element of length dℓ angular velocity = ω = (V/ℓ) hence

dE = Bωℓ dℓ

∴ Total emf = ^ℓ∫_O Bωℓ dℓ = [{Bωℓ²}/{2}]

∴ V_O – VA = [{Bωℓ²}/{2}]

V_O – VC = [{Bω(3ℓ)²}/ {2}]

From (1),
VA – VC = (9/2) Bωℓ² – [{Bωℓ²} /{2}] = 4 Bωℓ².
Question 7
4 / -1

Switch S of the circuit shown in figure is closed at t = 0. If e denotes the induced emf in L and i , the current flowing through the circuit at time t, which of the following graphs is correct?

A

B

C

D
Question 8
4 / -1

A device for generating and alternating current of a desired frequency is known as

A
an oscillator

B
an amplifier

C
a rectifier

D
none of these
Question 9
4 / -1

In an AC circuit containing only capacitance,the current

A
lags the voltage by 90º

B
leads the voltage by 90º

C
remains in phase with voltage

D
leads the voltage by 180º
Question 10
4 / -1

The rms value of emf of a saw totothed AC of peak voltage 60 volt is

A
60 √2 volt

B
60 /√2 volt

C
60 √3 volt

D
60 / √3 volt