Q1 Answer all of the following parts (a), (b), (c), etc. (a) Fig 20.36 shows a U-shaped magnet. Copy the diagram and show on it the magnetic field lines due to the magnet. (7)
(b) Why does a magnet that is free to rotate point towards the north? (7) (c) Draw a sketch of the magnetic field around a current-carrying solenoid. (7)
(d) A conductor of length 80 cm is carrying a current of 6 A. It is placed at right angles to a magnetic field of flux density 5 T. Calculate the force on the conductor. (7)
(e) State the principle on which the definition of the ampere is based. (7)
(f) Name one device that is based on the principle that a current-carrying conductor experiences a force in a magnetic field. (7)
(g) What is meant by electromagnetic induction? (7)
(h) A small magnet is attached to a spring as shown in Fig 20.37. The magnet is set oscillating up and down, first with switch A open, then with switch A closed.The magnet took longer to come to rest with the switch open. Why? (7)
(i) What is a transformer used for? (7)
(j) Why does greater current flow through a circuit containing an inductor when a d.c. power supply is used compared with an a.c. supply, given that the Vrms of the a.c. supply is equal to the d.c. voltage? (7)
‘SECTION B’
FULL QUESTIONS Q2 Define the ampere, the SI unit of current.
Describe an experiment to demonstrate the principle on which the definition of the ampere is based.
Calculate the force on the aluminium foil if its length is 40 cm and a current of 4.5 A flows through it when it is placed in a magnetic field of flux density 6.0 T.
Derive an expression for the force acting on a particle of charge q moving through a magnetic field of flux density B at a velocity v at right angles to the field.
Calculate the force on a proton moving at 2.5 104 m s1 at right angles to a magnetic field of flux density 200 T.The charge on a proton is 1.6 1019 C.
Q3 State Faraday’s law of electromagnetic induction. Describe an experiment to demonstrate Faraday’s law. State Lenz’s law of electromagnetic induction.
