Physics – Class 12 Practice Test 4

1. When an arc of a circle of radius R subtends an angle of \(\frac {\pi }{4}\) at the center, and carries a current I, the magnetic field at the center is B = \(\frac {\mu_o I}{16R}\).

2. Find the true statement.

3. Two parallel, long wires carry currents I₁ and I₂ where I₁ > I₂. When the currents are in the same direction, the magnetic field at a point midway between the wires is 50 μT. If the direction of I₂ is revered, the field becomes 100 μT. What is the value of \(\frac {I_1}{I_2}\)?

4. What should be the minimum magnitude of the magnetic field that must be produced at the equator of earth so that a proton may go round the earth with a speed of 1 × 10⁷ ms^-1? Earth’s radius is 6.4 × 10⁶ m.

5. Identify the factor on which the torque on a planar current loop does not depend.

6. Which among the following can be used to analyze circuits?

7. The frequency of revolution of a charged particle in a cyclotron does not depend on ‘X’. Identify X.

8. Electrons are accelerated in a cyclotron.

9. Find the false statement.

10. Identify the condition under which the force acting on a charge moving through a uniform magnetic field is maximum.