AC/DC With your partner complete the card sort game on symbols and terms.

Distinguish between alternating and direct current-D State the frequency and potential difference of UK mains electricity-C Describe how the potential of the live wires varies with each cycle-B Use oscilloscope traces to compare direct and alternating potential differences and measure the peak voltage of an ac source-A Measure the period and frequency of an ac source using an oscilloscope or diagrams of oscilloscope traces- A/A*

What are the similarities and differences between… Write down some ideas in your books

Distinguish between alternating and direct current-D DC stands for “Direct Current” – the current only flows in one direction: Time If the current flows in only one direction it is called direct current (DC). Batteries and cells supply DC electricity, with a typical battery supplying around 1.5 V. The diagram shows an oscilloscope screen displaying the signal from a DC supply.

Parts of a wave A CE B FD 1.Which letter shows the peak or crest of a wave? 2.Which letter shows the trough of a wave? 3.Which two letters represent the amplitude of a wave? 4.Which two letters represent the wavelength of a wave? Answers 1.C or E2. D or F 3. B and C4. C and E or D and F

Distinguish between alternating and direct current-D State the frequency and potential difference of UK mains electricity-C If the current constantly changes direction, it is called alternating current (AC). Mains electricity is an AC supply, with the UK mains supply being about 230 V. It has a frequency of 50 Hz (50 hertz), which means it changes direction, and back again, 50 times a second. The diagram shows an oscilloscope screen displaying the signal from an AC supply.

Describe how the potential of the live wires varies with each cycle-B On your laminated template add the wave for mains voltage and describe how the potential of the live wires varies with each cycle-B information to explaining a.c. current.

Use oscilloscope traces to compare direct and alternating potential differences and measure the peak voltage of an ac source-A Measure the period and frequency of an ac source using an oscilloscope or diagrams of oscilloscope traces- A/A* The period of an AC supply is the time taken for one complete oscillation. You can find this by looking at the time between one peak and the next, between one trough and the next, or between any two identical places on adjacent oscillations. In the oscilloscope trace on this page, one horizontal division represents 5 ms (five milliseconds). There are four divisions between two adjacent peaks, so the period is: 4 × 5 = 20 ms

Use oscilloscope traces to compare direct and alternating potential differences and measure the peak voltage of an ac source-A Measure the period and frequency of an ac source using an oscilloscope or diagrams of oscilloscope traces- A/A* Frequency The frequency of an AC supply is the number of oscillations per second. You can find it from the period: Frequency = 1 ÷ period (Equation is not given on formula sheet) Remember to convert to seconds if needed. In this example, 20 ms = 20 ÷ 1000 = s. Frequency = 1 ÷ = 50 Hz UK mains frequency is 50 Hz but you may get other frequencies (and periods) to calculate in the examination.

Discuss in pairs whether d.c. or a.c. is used for the following devices, giving reasons: iPod bedside lamp clock radio wall clock television remote control microwave

Discuss in pairs whether d.c. or a.c. is used for the following devices, giving reasons: iPod (DC) bedside lamp (AC) clock radio (AC) wall clock (DC) television remote control (DC) microwave(AC)

AC and DC Copy the diagrams Describe what happens in AC and DC circuits in a few sentences, referring to electron flow

Distinguish between alternating and direct current-D State the frequency and potential difference of UK mains electricity-C Describe how the potential of the live wires varies with each cycle-B Use oscilloscope traces to compare direct and alternating potential differences and measure the peak voltage of an ac source-A Measure the period and frequency of an ac source using an oscilloscope or diagrams of oscilloscope traces- A/A*