ELECTRICITY (IGCSE 2011)

0625/31/M/J/11 5 The manufacturer’s label on an electric heater is as shown in Fig. 5.1.

4 The circuit of Fig. 4.1 is set up to run a small immersion heater from a 6.0 V battery.

Fig. 5.1

(a) State what electrical quantity is represented by

(i) 110 V,
(ii) 60 Hz,
(iii) 1 kW. [1]

Fig. 4.1 (b) (i) Which part of the electric heater must be earthed?
(a) State the name and purpose of component X. [1]
name
(ii) Explain what the hazard might be if the heater is not earthed.
purpose [1]

(b) The heater is designed to work from a 3.6 V supply. It has a power rating of 4.5 W at
this voltage. [2]
(i) Calculate the current in the heater when it has the correct potential difference across
it. [2] (c) The heater has two 110 V heating elements, with two switches, so that either one or
both elements may be switched on.
In the space below, draw a circuit diagram showing how the heating elements and
switches are connected to the mains supply.
(ii) Calculate the resistance of component X if there is to be the correct potential Use the symbol for each heating element.
difference across the heater. The battery and the ammeter both have zero resistance.
[3]

(c) Some time after the heater is switched on, the ammeter reading is seen to have
decreased. Suggest why this happens.

[1]
(d) As an alternative to running the heater from a battery, it is decided to construct a
circuit to enable it to be operated from the a.c. mains supply.
Name the electrical component needed to
(i) reduce the potential difference from that of the mains supply down to a potential
difference suitable for the heater,
[1]
(ii) change the current from a.c. to a current which has only one direction. [2]
[1] [Total: 6]
[Total: 9]
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ELECTRICITY (IGCSE 2011)
0625/32/M/J/11 10 (a) In the space below, draw the symbol for an OR gate. [1]
8 (a) What is meant by the electromotive force (e.m.f.) of an electric power supply?

[2]
(b) When connected to a 240 V supply, a desk lamp has a power rating of 60 W.
Calculate
(i) the current in the lamp, [2]
(b) Describe the action of an OR gate in terms of its inputs and outputs.

(ii) the resistance of the lamp’s filament. [2]

[2]

(c) A car manufacturer wishes to install an alarm system in a 2-door car to inform the
driver if either door is not properly closed. An OR gate is to be used in the construction
(c) A torch lamp is normally connected to a 3.0 V battery and carries a current of 0.25 A. of this system.
The resistance of its filament is 12 Ω. Describe suitable input and output arrangements for the gate.
The desk lamp in (b) and the torch lamp are connected in series.
Students X and Y plan to connect the lamp combination to a 240 V supply.
Student X says that the filament of the torch lamp will melt and the circuit will no
longer work.
Student Y says that both lamps will light up and stay on.
Show, with a suitable calculation, whether student X or student Y is correct.
[3]
[Total: 6]

[2]
[Total: 8]
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ELECTRICITY (IGCSE 2011)
0625/31/O/N/11 0625/32/O/N/11
9 The graphs in Fig. 9.1 show the relation between the current I and the potential 9 Fig. 9.1 shows a circuit containing a battery, three resistors and an ammeter.
difference V for a resistor and a lamp.

Fig. 9.1

(a) (i) Write down the equation for the effective resistance Rp of two resistors of
Fig. 9.1 resistances R1 and R2 connected in parallel.

(a) (i) Describe how, if at all, the resistance varies as the current increases in (ii) Use this equation to calculate the effective resistance of the two resistors in parallel in
1. the resistor, ............................................................................................................. Fig. 9.1. [2]
2. the lamp. ................................................................................................................ [2]

(ii) State the value of the potential difference when the resistor and the lamp have the
(b) A voltmeter is to be used to measure the potential difference across the resistors in
same resistance. Potential difference = …………………………..[1] parallel.
(i) On Fig. 9.1, draw the voltmeter in position in the circuit, using the correct circuit symbol.
(b) The two components are connected in parallel to a supply of e.m.f. 4.0 V. Calculate
(ii) The ammeter reads 1.6 A. Calculate the reading on the voltmeter. [3]
the total resistance of the circuit. [4]

(c) State what happens to the ammeter reading if the 1 Ω resistor is replaced by a 3 Ω
resistor.

[1]
[Total: 6]
[Total: 7]
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ELECTRICITY (IGCSE 2011)
0625/33/O/N/11 10 Fig. 10.1 shows schematically a digital electronic circuit.
7 Fig. 7.1 shows a circuit containing a 12 V power supply, some resistors and an
ammeter whose resistance is so small that it may be ignored.

Fig. 10.1

(a) State the name of the logic gate

(i) at A,
(ii) at B. [2]

Fig. 7.1
(b) The light sensor has a “high” (logic 1) output in bright light and a “low” (logic 0) output
(a) (i) Determine the potential difference across the 2 Ω resistor. [1] when it is dark.
The heat sensor has a “high” (logic 1) output when it is hot and a “low” (logic 0) output
when it is cold.
(ii) State the potential difference across the 3 Ω resistor. .......................................... [1] State the outputs of A and B when
(b) Calculate the effective resistance of (i) it is bright and cold,
(i) the 2 Ω and 4 Ω resistors connected in series, [1] output of A =
output of B =
(ii) it is dark and hot.
(ii) the 3 Ω and 6 Ω resistors connected in parallel. [2] output of A =
output of B = [4]

(c) Suggest why B is connected to a relay in order to light the lamp.

(c) Calculate the reading on the ammeter. [2]

[1]

(d) Suggest a practical use for this circuit.

(d)Without further calculation, state what happens, if anything, to the ammeter reading if
(i) the 2 Ω resistor is shorted out with a thick piece of wire,
........................................................................................................................................... [1]
(ii) the thick piece of wire from (d)(i) and the 3 Ω resistor are both removed. [Total: 8]
....................................................................................................................................... [2]
[Total: 9]

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