N1 Engineering Science|The Easy Way! 123 Exercise 6.6 1. What do you understand by power?
2. What is the unit in which power is measured? 3. How does the supply voltage affect the power consumption of a circuit?
4. Describe the relationship that exists between potential difference, current and power.
5. Calculate the power consumption of a 12 volt electric soldering iron when it draws 5 amperes at rated voltage.
6. A current of 1,5 amperes flows through the filament of a 12 volt lamp. What is the power rating of the lamp?
7. A certain lamp draws 0,273 amperes when connected to a 220 volt supply. Determine the power rating of the lamp.
9. An incandescent lamp is rated at 220 volts, 100 watts. Determine the rated current.
(60 W) (18 W) (60,06 W)
8. When a current of 3 amperes flows through an incandescent lamp, the power consumption is 60 watts. Determine the supply voltage across the lamp. (20 V)
(0,455 A)
10. A geyser element is rated at 220 volts, 3 kW. What current will it draw from the supply?
11. If a lamp is rated to draw 1,5 amperes and consume 18 watts, what is the correct supply voltage?
12. An electric griller has a label indicating 2 440 watts and 220 volts. How much current will it draw when connected to the supply?
(13,64 A) (12 V) (11,09 A)
13. When a current of 3,2 amperes flows through a resistance element, the power consumption is 25 watts. What is the pd across the element?
14. What is the power rating of a 220 volt electric kettle if it draws 4,55 amperes from the supply?
15. What current should a 220 volt, 60 watt incandescent lamp draw from the supply?
(7,813 V) (1 001 W = 1 kW) (0,272 7 A)
16. What is the voltage rating of a 36 watt globe if it draws a current of 3 amperes from the rated supply?
(12 V)
17. A certain lamp has a resistance of 9,6 ohms and draws a current of 2,5 amperes when connected across the correct supply voltage. Determine; 17.1 the power, and 17.2 the voltage rating of the lamp.
18. A 220 volt electric iron is rated at 800 watts. Calculate; 18.1 the current it would draw from the supply, and 18.2 the resistance of the element.
(60 W; 24 V) (3,636 A; 60,51 ohms)
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