End A of the rod is joined to the positive terminal of a d.c. power supply, while B is connected to the negative terminal. The current in the rod and the magnetic field together create a force on the rod. On Fig. 7.1, draw arrows to indicate (i) the direction of the current in the metal rod; label this arrow C, (ii) the direction of the magnetic field acting on the metal rod; label this arrow M, (iii) the direction of the force on the rod; label this arrow F.
The power supply is taken away and a sensitive voltmeter is connected across ends A and B. When the rod is moved up or down, the voltmeter gives a reading. Explain why the voltmeter shows a reading.
The voltmeter reading can also be raised by using a stronger magnetic field. State one other way to produce a larger voltmeter reading.