A student is investigating the electrical properties of different components and materials.
The student sets up a series circuit containing a 12 V d.c. power supply, an ammeter, a variable resistor, a switch, and two open terminals, P P\,P and QQQ. They place different materials across the terminals P P\,P and Q Q\,Q to test their conductivity.
State the purpose of the variable resistor in this circuit.
Explain how the student can tell if a material is a conductor of electricity using this circuit.
Identify the good conductors of electricity from the following list: aluminum, wood, brass, rubber, glass.
The student now connects a small filament lamp in the gap between P P\,P and Q Q\,Q to determine its resistance.
Name the additional meter needed to measure the potential difference required for this determination.
State how this meter must be connected in the circuit.
An electric room heater contains three identical heating elements that operate at full power when connected across a 240 V mains supply.
The electric heater has two switches: the first switch controls one heating element, and the second switch controls the other two heating elements together. Describe how the two heating elements controlled by the second switch should be connected to ensure they both receive the full 240 V when switched on.
When a single heating element is operating, the current through it is 3.0 A from the 240 V supply. Calculate the electrical resistance of one heating element, stating the correct unit.
When all three elements are switched on at the same time, which statement about the total resistance of the heater is correct?
136 exam-style questions on CIE IGCSE Physics 4.3 Electric circuits, covering 4.3.1a Circuit diagrams and circuit components, 4.3.2a Series circuits, 4.3.2b Parallel circuits, 4.3.2c Current and potential difference in circuits, 4.3.2d Combined resistance of resistors in parallel, and 4.3.3 Action and use of circuit components. Each one has a worked solution and a mark scheme showing where the marks go.