Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.4 Using mains electricity safely and the power of electrical appliances_1 Key Recall Question Answer 1. What is direct current (d.c.)? Current that always passes in the same direction. 2. What sorts of power supplies produce Cells and batteries. direct current? 3. What is alternating current (a.c.)? Current which is constantly changing direction. 4. What sort of supplies produce Main electricity. alternating current? 5. What sort of electricity is represented by a.c. this oscilloscope trace? 6. If the above oscilloscope trace represents 1 2 cycles per second (hertz) second, what is the frequency of the supply? 7. What is the frequency and potential 50 and 230 V (approx) difference of electricity? 8. How are most electrical appliances cable and three pin plugs. connected to electricity? 9. two wires are always found in Live and neutral electrical cables? 10. third wire is often found in electrical Earth cables? 11. Why do some wires not have an Earth Because the appliance they are attached to have plastic wire? casing (double insulated) or the live wire cannot touch the casing. Therefore they cannot cause electric shocks. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3
Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3 4 5 6 7 8 9 P2.4 Using mains electricity safely and the power of electrical appliances_1 Key Recall Question Answer 1. What is direct current (d.c.)? Current that always passes in the same direction. 2. What sorts of power supplies produce direct current? Cells and batteries. 3. What is alternating current (a.c.)? Current which is constantly changing direction. 4. What sort of supplies produce alternating current? Main electricity. 5. What sort of electricity is represented by this oscilloscope trace? a.c. 6. If the above oscilloscope trace represents 1 second, what is the frequency of the supply? 2 cycles per second (hertz) 7. What is the frequency and potential difference of electricity? 50 and 230 V (approx) 8. How are most electrical appliances connected to electricity? cable and three pin plugs. 9. two wires are always found in electrical cables? Live and neutral 10. third wire is often found in electrical cables? Earth 11. Why do some wires not have an Earth wire? Because the appliance they are attached to have plastic casing (double insulated) or the live wire cannot touch the casing. Therefore they cannot cause electric shocks. Question Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: Date: 1 2 3