Question

1. A proton is accelerated through a potential difference of 10 kV and enters a uniform magnetic field at right angles. Calculate the value of the magnetic flux density necessary to move the proton in a circular path of radius 10 mm. [6]

2. A piece of wire of cross-sectional area A and resistivity ρ is bent into a circular loop of radius r and placed in a magnetic field with its plane at right angles to the field. Determine the magnitude of the current in the loop if the field is reduced to zero in time t. [5]

3. A 40 μF capacitor is charged to a voltage of 120 V. How much work must be done to transfer 60 μC from the negative plate to the positive? [5]

4. A point charge of magnitude +q and speed v is located at a distance d from a long straight wire carrying a current I.

(a) Determine the magnitude of the force on the charge if it is moving directly towards the wire. [3]

(b) Is the direction of the force parallel or anti-parallel to the wire? Use a fully labeled sketch to motivate your answer. [3]

Answer 1