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Electric circuits 1
Symbol
Name
Description of how it works.
Open switch
Breaks the circuit. No
current flows. Incomplete
circuit
Closed circuit
Completes the circuit.
Current flows.
Lamp
Current flows through
giving off charge and
lighting the lamp
Cell
Battery
Lots of cells together
voltmeter
Measures potential
difference
Resistor
Fuse
Ammeter
Measures current
Variable resistor
Thermistor
As the temperature goes
up, the resistance goes
down
Light dependant resistor
As light intensity goes up,
resistance goes down
1) On the table, draw the symbol, write its name and give a brief
description of what is does.
1. What electrical component does this circuit symbol represent?
…………………LDR – light dependant resistor…..(1 mark)
2. In this circuit there are three light bulbs connected to the same
battery. If one of the bulbs blew, what would happen to the other
bulbs?
……………stay lit with same brightness……………
………………………………………………………………..(1 mark)
3. Which of these ammeters is wired correctly and why?
…………C – ammeters must be wired in series………
………………………………………………………………..(2 marks)
4. What is the reading on the ammeter labelled A1 in this circuit?
…………0.4 = 0.3 + A1 A1 = 0.1…………………
………………………………………………………………..(2 marks)
S
A
A
B
V
V
5.
a.i. On the above circuit, draw an ammeter to measure the
current going through the second lamp. (1 mark)
ii. On the above circuit, draw two voltmeters to measure the
potential difference of the two lamps. (1 mark)
iii. On the above circuit, mark where the best place to insert a
switch is. Label it S. (1 mark)
b.i. Once you had found the current and potential difference, how
could you calculate the resistance of the two lamps?
……V = IR R = V/I…………(1 mark)
ii. The current flowing round the circuit was found to be 0.15A.
The potential difference across lamp A was 1.5V. What is the
resistance of lamp A? Show all working.
…… R = V/I R = 1.5/0.15 = 10 Ohms
……………………………………………………………..(2 marks)
6 The circuit shown has four identical ammeters.
(a) The table gives the current through two of the ammeters.
0.5
0.5
(i) Complete the table to show the current through the other two
ammeters. (2 marks)
(ii) Which one of the following statements is correct. Tick (√) the
box next to your choice.
The resistance of P is more than 20 Ω.
The resistance of P is equal to 20 Ω.
The resistance of P is less than 20 Ω.
Give a reason for your choice.
√
more current is flowing through the 20 Ohm resistor than P. Given
that R = V/I with less current there is more resistance
(2 marks)
(b) (i) Write down the equation that links current, potential
difference and resistance.
.....V = IR (1 mark)
(ii) Calculate the reading on the voltmeter. Show clearly how you
work out your answer.
V = 20 x 0.3 = 6
Voltmeter reading = .........6.................... volts.
(2 marks)
(iii) State the potential difference of the power supply.
................... 6 V ...........................................
(1 mark)
(c) A second circuit contains an unknown component labelled X.
As component X is heated, the reading on the ammeter goes up.
What is component X?
............Thermistor...........................
Give a reason for your answer.
resistance goes down (as temperature of thermistor goes up)
(2 marks)