Q6 Answer all of the following parts (a), (b), (c), etc. (a) Define resistance. (7)
(b) Name the electrical component represented in Fig 18.34. (7)
(c) Give two uses for the instrument shown. (7)
(d) Christmas tree lights used to be connected in series but are now connected in parallel.What are the two main advantages to this change? (7)
(e) What is a potentiometer? (7) (f) Name the electrical component represented in Fig 18.35. (7) (g) Define resistivity. (7)
(h) Explain why the resistance of a light bulb is different when it is not connected to the mains compared with when it is. (7)
(i) What are the charge carriers when an electric current (i) passes through a metal; (ii) passes through an electrolyte? (7)
(j) Give a practical use of a Wheatstone bridge, other than for measuring resistance. (7)
Fig 18.35 Instrument to be identified in 6 (c)
Fig 18.34
‘SECTION B’
FULL QUESTION Q7 Name an instrument used to measure resistance.
Fig 18.36 shows a circuit diagram consisting of two resistors connected in series with a 12 V battery. Calculate: (i) the total resistance of the circuit (6) (ii) the current in the circuit (6) (iii) the potential difference across the 6 resistor. (6)
12 V
The arrangement of the circuit was changed so that the resistors were placed in parallel, as shown in Fig 18.37 on the next page. Calculate: (iv) the total resistance of the two resistors (9) (v) the current flowing in the circuit (6)
