The magnetic field at the centre of a 50 cm long solenoid is 4 . 0 × 10 - 2 T when a current of 8 . 0 A flows through it. What is the number of turns in the solenoid? Take π = 3 . 14 .

Given: The length of solenoid, l = 50 cm = 0 . 5 m The magnetic field at the centre, B = 4 . 0 × 10 - 2 T Current in the solenoid, I = 8 . 0 A We know the magnetic field inside the solenoid is given as, B = μ 0 n I , Where n is number of turns per unit length. If N is the total number of turns, then n = N l ∴ B = μ 0 n I = μ 0 N l I ⇒ N = B l μ 0 I = 4 .0 × 10 − 2 × 0 .50 4 × 3 .14 × 10 − 7 × 8 = 1990

An ‐particle of mass 6 . 65 × 10 - 27 kg and charge twice that of an electron but of positive sign travels at right angles to a magnetic field with a speed of 6 × 10 5 m s - 1 . The strength of the magnetic field is 0 . 2 T . (i) Calculate the force on the ‐particle. (ii) Also calculate its acceleration.

Given: The mass of α -particle, m = 6 .65 × 10 27 kg The speed of α -particle, v = 6 × 10 5 ms - 1 The strength of the magnetic field, B = 0 . 2 T Angle between magnetic field and velocity vector, θ = 90 ° We know the charge on α -particle, q = + 2 e = 2 × 1 .6 × 10 − 16 C The force on a moving charge in an uniform magnetic field is given as, F = q v B sin θ F = q v B sin sin 90 ∘ = 2 × 1 .6 × 10 − 19 × 6 × 10 5 × 0 .2 × 1 N = 3 .84 × 10 − 14 N From Newton’s second law of motion F = m a ⇒ a = E m = 3 6 84 65 × 10 − 14 × 10 − 22 = 5 .77 × 10 12 ms − 2

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IMPORTANT

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A long solenoid is made by closely winding a wire of radius $0.5 mm$ over a cylindrical non‐magnetic frame so that successive turns nearly touch each other. What will be the magnetic field at the centre of the solenoid if a current of $5 A$ flows through it?

Important Questions on Magnetic Effect of Current

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems for Practice>Q 3

The magnetic field at the centre of a

50 cm

long solenoid is

4.0 \times 10^{- 2} T

when a current of

8.0 A

flows through it. What is the number of turns in the solenoid? Take

π = 3.14

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems for Practice>Q 4

A solenoid is

1.0 m

long and

3.0 cm

in diameter. It has five layers of windings of

850

turns each and carries a current of

5.0 A

. (i) What is

B

at its centre? (ii) What is the magnetic flux

ϕ_{B}

for a cross‐section of the solenoid at the centre?

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems for Practice>Q 5

A solenoid is

2.0 m

long and

3.0 cm

in diameter. It has

5

layers of winding of

1000

turns each and carries a current of

5.0 A

. What is the magnetic field at the centre? Use the standard value of

μ_{0}

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems for Practice>Q 6

A toroid has a core of inner radius

20 cm

and outer radius

22 cm

around which

4200

turns of a wire are wound. If the current in the wire is

10 A

, what is the magnetic field (i) inside the core of toroid (ii) outside the toroid and (iii) in the empty space surrounded by the toroid.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems for Practice>Q 7

A long straight solid conductor of radius

4 cm

carries a current of

2 A

, which is uniformly distributed over its circular cross‐section. Find the magnetic field at a distance of

3 cm

from the axis of the conductor.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 1

An electron moving with a velocity of

5.0 \times 10^{- 7} {ms}^{- 1}

enters a magnetic field of

1.0 W b m^{- 2}

at an angle of

30 °

. Calculate the force on the electron.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 2

An ‐particle of mass

6.65 \times 10^{- 27} kg

and charge twice that of an electron but of positive sign travels at right angles to a magnetic field with a speed of

6 \times 10^{5} m s^{- 1}

. The strength of the magnetic field is

0.2 T

.
(i) Calculate the force on the ‐particle. (ii) Also calculate its acceleration.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 4 - Magnetic Effect of Current>Problems For Practice>Q 3

An electron is moving northwards with a velocity of

10^{7} {ms}^{- 1}

in a magnetic field of

3 T

, directed downwards. Calculate the instantaneous force on the electron.

A long solenoid is made by closely winding a wire of radius 0.5 mm over a cylindrical non‐magnetic frame so that successive turns nearly touch each other. What will be the magnetic field at the centre of the solenoid if a current of 5 A flows through it?

Important Questions on Magnetic Effect of Current

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A long solenoid is made by closely winding a wire of radius $0.5 mm$ over a cylindrical non‐magnetic frame so that successive turns nearly touch each other. What will be the magnetic field at the centre of the solenoid if a current of $5 A$ flows through it?