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**Q.1. A short electric dipole has a dipole moment of 16×10 ^{-9} C m. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of 60° with the dipole axis is: (2020)**

A: 400 V

B: Zero

C: 50 V

D: 200 V

Ans:

A: Increases as r increases for both r < R and r > R

B: Zero as r increases for r < R, decreases as r increases for r > R

C: Zero as r increases for r < R, increases as r increases for r > R

D:

Answer:

By Gauss law,

⇒ E

A: Zero

B:

C:

D:

Answer:

Electric field due to line charge (1)

Electric field due to line charge (2)**Q.4. Two point charges A and B, having charges +Q and –Q respectively, are placed at certain distance apart and force acting between them is F. If 25% charge of A is transferred to B, then force between the charges becomes : (2019)A: FB: 9F/16C: 16F/9D: 4F/3Answer:** B

If 25% of charge of A transferred to B then

A: smaller

B: 5 times greater

C: 10 times greater

D: equal

Answer:

A: 2 m/s, 4 m/s

B: 1 m/s, 3 m/s

C: 1 m/s, 3.5 m/s

D: 1.5 m/s, 3 m/s

Answer:

0 < t < 1s : velocity increases from 0 to 6 m/s

1 < t < 2s : velocity decreases from 6 to 0 m/s

but car continues to move forward

2 < t < 3s : since field strength is same ⇒ same acceleration

∴ car's velocity increases

from 0 to –6 m/

B: v ∝ x

C: v ∝ x

D: v ∝ x

Answer:

A:

B:

C:

D:

Solution:

A:

B:

C:

D:

Answer:

Solution:

A:

C:

D:

Answer:

Solution:

A:

B:

C: zero

D:

Answer: A

B:

C:

D:

Answer:

Solution:

Net magnetic moment will be maximum if cos θ is maximum.

cos θ will be maximum when θ will be minimum. So, at θ = 30º m

The direction of magnetic moment is from S to N

Net magnetic moment will be maximum if cos θ is maximum.

cos θ will be maximum when θ will be minimum. So, at θ = 30º m

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