Physics WAEC / WASSCE 2010 Electricity and Magnetism
You are provided with a voltmeter V, a chemical cell/ battery E; two standard resistors R, and R a potentiometer a key K a jockey, and other necessary materials. Set up a circuit as shown in the diagram above. Close the key K. Make contact with the potentiometer wire AB using the jockey at a point C such that AC = x = 20cm Read and record the voltmeter reading Evaluate x\(^{-1}\) and v\(^{-1}\) Repeat the procedure for other values of x= 30, 40, 50, 60 and 80cm. Tabulate your readings. Plot a graph with V\(^{-1}\) on the vertical axis and x\(^{-1}\) on the horizontal axis, starting both axes from the origin (0, 0). Determine the: (a) slope, s, of the graph; (b) intercept, c, on the vertical axis. State two precautions taken to ensure accurate results. (b)i. State the two devices in which ohm's law does not apply. ii. A current of 1 A is supplied to two resistors of resistance 2\(\Omega\) and 3\(\Omega\) connected in parallel. Calculate the current in each resistor.