NEET Magnetic Effects of Current and Magnetism — Set 9

Question 1

A square loop of side $ 0.16 \, \text{m} $ with 25 turns carries $ 3 \, \text{A} $ in a magnetic field of $ 0.7 \, \text{T} $. The plane of the loop is at $ 45^\circ $ to the field. What is the torque?

Accepted Answer

Torque $ \tau = N I A B \sin \theta $, where $ A = 0.16 \times 0.16 = 0.0256 \, \text{m}^2 $. $ \tau = 25 \times 3 \times 0.0256 \times 0.7 \times \sin 45^\circ = 1.344 \times 0.707 = 0.9502 \approx 0.95 \, \text{N m} $.

Question 2

A long straight wire carries a current of $ 25 \, \text{A} $. What is the magnetic field at a distance of $ 0.25 \, \text{m} $ from it? ($ \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} $)

Accepted Answer

Magnetic field $ B = \frac{\mu_0 I}{2 \pi r} $. $ B = \frac{4 \pi \times 10^{-7} \times 25}{2 \pi \times 0.25} = \frac{100 \times 10^{-7}}{0.5} = 2 \times 10^{-5} \, \text{T} $.

Question 3

A solenoid has 2000 turns per meter and carries a current of $ 3 \, \text{A} $. What is the magnetic field inside it? ($ \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} $)

Accepted Answer

Magnetic field $ B = \mu_0 n I $. $ B = 4 \pi \times 10^{-7} \times 2000 \times 3 = 12 \pi \times 10^{-4} \approx 7.54 \times 10^{-3} \, \text{T} $.

NEET Physics: Magnetic Effects of Current and Magnetism — Practice Set 9

Q1. A square loop of side \( 0.16 \, \text{m} \) with 25 turns carries \( 3 \, \text{A} \) in a magnetic field of \( 0.7 \, \text{T} \). The plane of the loop is at \( 45^\circ \) to the field. What is the torque?

Q2. A long straight wire carries a current of \( 25 \, \text{A} \). What is the magnetic field at a distance of \( 0.25 \, \text{m} \) from it? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q3. A solenoid has 2000 turns per meter and carries a current of \( 3 \, \text{A} \). What is the magnetic field inside it? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q4. A proton moves with a speed of \( 1.8 \times 10^6 \, \text{m/s} \) perpendicular to a magnetic field of \( 0.5 \, \text{T} \). What is the radius of its path? (Mass = \( 1.67 \times 10^{-27} \, \text{kg} \), charge = \( 1.6 \times 10^{-19} \, \text{C} \))

Q5. What is the role of the magnetic field in a moving coil galvanometer?

Q6. What is the direction of the magnetic force on a positive charge moving parallel to a uniform magnetic field?

Q7. A solenoid has 800 turns per meter and carries a current of \( 2.5 \, \text{A} \). What is the magnetic field inside it? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q8. What is the nature of the force between two parallel wires carrying currents in opposite directions?

Q9. A long wire carries \( 18 \, \text{A} \). At what distance is the magnetic field \( 6 \times 10^{-6} \, \text{T} \)? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))

Q10. A circular coil of 80 turns and radius \( 4 \, \text{cm} \) carries a current of \( 0.5 \, \text{A} \). What is the magnetic field at its center? (\( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \))