Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 744 · 40 questions

Remember (Find the topic, use the formula): Find the topic and the formula: V = I × R, I = V ÷ R, R = V ÷ I, P = V × I, units = W × h ÷ 1000. Change mA to A and kΩ to Ω before using a formula. Check: put your answer back into the formula.

1. 1.🔍 Which is the odd one out? (a) use old filament bulbs (b) use LED lamps (c) switch off empty rooms (d) use daylight to read
2. 2.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) the size of a cell (d) energy used each second
3. 3.True or false: to close the fridge quickly wastes electricity. (a) False (b) True
4. 4.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
5. 5.🧮 A 10 V battery is joined to 10 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
6. 6.⚡ A 1.5 W device works on 6 V. What current does it take (in amperes)? =
7. 7.True or false: to unplug idle chargers wastes electricity. (a) True (b) False
8. 8.True or false: to use old filament bulbs saves electricity. (a) True (b) False
9. 9.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
10. 10.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
11. 11.True or false: an LDR senses how bright it is. (a) False (b) True
12. 12.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 740 Ω resistor? (a) violet-yellow-red (b) violet-yellow-brown (c) violet-yellow-black (d) yellow-violet-brown
13. 13.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
14. 14.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
15. 15.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) less than either one (d) more than either one
16. 16.True or false: the voltmeter measures voltage. (a) True (b) False
17. 17.📏 How many watts (W) is 3.2 kW?
18. 18.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
19. 19.💡 An LED is joined to a 9 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) lights up (c) does not light
20. 20.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
21. 21.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
22. 22.🌈 A resistor has the colour bands green, yellow, red. What is its value in kilo-ohms (kΩ)? =
23. 23.📏 How many milliamperes (mA) is 1.86 A?
24. 24.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
25. 25.🧮 A 220 Ω resistor is joined in series with two equal 200 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
26. 26.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
27. 27.Which of these is measured in watts (W)? (a) resistance (b) the flow of charge (c) power (d) how much a part resists
28. 28.🧩 Which component makes a beeping sound? (a) resistor (b) capacitor (c) motor (d) buzzer
29. 29.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
30. 30.💡 Does it save or waste electricity to use daylight to read? (a) saves electricity (b) wastes electricity
31. 31.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🔺 A current of 0.1 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🔺 A current of 2.5 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 46 Ω resistor? (a) yellow-blue-brown (b) green-blue-black (c) blue-yellow-black (d) yellow-blue-black
35. 35.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
36. 36.🌈 In the resistor colour code, which number does orange stand for?
37. 37.Which of these saves electricity? (a) leave the TV on standby (b) run fans in empty rooms (c) use daylight to read (d) iron one shirt at a time
38. 38.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 18 Ω resistor? (a) grey-brown-black (b) red-grey-black (c) brown-grey-black (d) brown-grey-brown
39. 39.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🌈 A resistor has the colour bands blue, brown, red. What is its value in kilo-ohms (kΩ)? =

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