UNIT 4 – PHYSICAL WORLD Potential difference


The difference in charge between the two terminals of a battery is what creates the potential for electrons to flow. This potential difference is also known as voltage. Voltage is what pushes the current around a circuit.


The SI unit of voltage is the volt (V). The instrument used to measure voltage is a voltmeter.


An electrical circuit is a closed path which contains electrical components that current can flow through. As voltage pushes electrons around a circuit, their energy is divided among the components, e.g. bulbs. The more components there are in a circuit, the more voltage is used. The battery supplies the potential difference to move electrons while the circuit is closed.


Batteries have different values of voltage. The greater a battery’s voltage, the greater the push of electrons.


: Fig. 30.3 A voltmeter ? TEST TUBE


3. What other term is used for voltage? 4. Research the following batteries, then copy and complete the following table.


Battery shape AA


A23


CR2025 CR-P2


Circuits Circuit diagrams


When scientists sketch electrical circuits, they use symbols that are easy to draw and recognise, to represent measuring instruments and components such as batteries, bulbs and switches.


The table shows the most common symbols used in circuit diagrams. These symbols are also given in the Formulae and Tables booklet, which you will have in your final exam.


The components in a circuit can be connected in series or in parallel.


Component Battery Bulb Switch (off and on)


Resistor (fixed or variable)


Ammeter Voltmeter Ohmmeter A V  Circuit symbol ( Fig. 30.4 ( Fig. 30.5 ( Fig. 30.6 ( Fig. 30.7 ( Fig. 30.8 ( Fig. 30.9 ( Fig. 30.10


Voltage (V) 1.5


Example of use


294 Elements of Science


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