NEET Magnetic Effects of Current and Magnetism — Set 1

Question 1

What is the effect on the magnetic force if a charged particle’s velocity is doubled while keeping the magnetic field constant?

Accepted Answer

The magnetic force $ F = q v B \sin \theta $ is directly proportional to velocity $ v $. Doubling the velocity doubles the force.

Question 2

A solenoid with 1200 turns per meter carries $ 1 \, \text{A} $. What is the magnetic field inside? ($ \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} $)

Accepted Answer

$ B = \mu_0 n I $. $ B = 4 \pi \times 10^{-7} \times 1200 \times 1 = 4.8 \pi \times 10^{-4} \approx 1.51 \times 10^{-3} \, \text{T} $.

Question 3

In a current-carrying loop placed in a magnetic field, when is the torque maximum?

Accepted Answer

The torque on a current-carrying loop in a magnetic field is given by $ \tau = N I A B \sin \theta $. It is maximum when $ \sin \theta = 1 $, i.e., $ \theta = 90^\circ $, meaning the plane of the loop is perpendicular to the magnetic field.

NEET Physics: Magnetic Effects of Current and Magnetism — Practice Set 1

Q1. What is the effect on the magnetic force if a charged particle’s velocity is doubled while keeping the magnetic field constant?

Q2. A solenoid with 1200 turns per meter carries \( 1 \, \text{A} \). What is the magnetic field inside? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q3. In a current-carrying loop placed in a magnetic field, when is the torque maximum?

Q4. Two parallel wires \( 0.04 \, \text{m} \) apart carry \( 5 \, \text{A} \) and \( 7 \, \text{A} \) in opposite directions. What is the force per unit length? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q5. A wire of length \( 1.9 \, \text{m} \) carrying \( 4.5 \, \text{A} \) is at \( 45^\circ \) to a magnetic field of \( 0.3 \, \text{T} \). What is the force on the wire?

Q6. A solenoid has 950 turns per meter and carries a current of \( 1.4 \, \text{A} \). What is the magnetic field inside it? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q7. An electron moves at \( 4.5 \times 10^6 \, \text{m/s} \) perpendicular to a field of \( 0.35 \, \text{T} \). What is the magnetic force? (Charge = \( 1.6 \times 10^{-19} \, \text{C} \))

Q8. A circular loop of radius \( 0.09 \, \text{m} \) with 45 turns carries a current of \( 1.2 \, \text{A} \). What is the magnetic field at the center? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q9. Why is the magnetic field outside a long solenoid considered negligible?

Q10. A square loop of side \( 0.18 \, \text{m} \) with 30 turns carries \( 2 \, \text{A} \) in a magnetic field of \( 0.4 \, \text{T} \). The plane of the loop is at \( 60^\circ \) to the field. What is the torque?