Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 177 · 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.⚡ A 1.25 W device works on 5 V. What current does it take (in amperes)? =
2. 2.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a filament bulb (c) an LED lamp (d) a candle
3. 3.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
4. 4.True or false: current is measured in ohms (Ω). (a) True (b) False
5. 5.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
6. 6.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = R ÷ V (d) I = V ÷ R
7. 7.💡 An LED is joined to a 5 V battery through a 220 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
8. 8.🌈 A resistor has the colour bands grey, red, yellow. What is its value in kilo-ohms (kΩ)? =
9. 9.🔍 Which is the odd one out? (a) leave the TV on standby (b) iron one shirt at a time (c) unplug idle chargers (d) use old filament bulbs
10. 10.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
11. 11.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
12. 12.🧮 A 22 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
13. 13.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) always zero (d) their sum
14. 14.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 60 (d) 1000
15. 15.📏 Which unit measures power? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
16. 16.🔺 A current of 2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🔺 A current of 0.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
18. 18.📏 Which unit measures current? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
19. 19.🧩 Which component has coloured bands? (a) transistor (b) resistor (c) LDR (d) potentiometer
20. 20.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
21. 21.🧮 Resistors of 10 Ω, 22 Ω, 20 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
22. 22.🔺 A current of 2.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.🌈 A resistor has the colour bands grey, white, brown. What is its value (in ohms)?
24. 24.🌈 A resistor has the colour bands white, yellow, orange. What is its value (in ohms)?
25. 25.True or false: current is measured in amperes (A). (a) True (b) False
26. 26.🌈 In the resistor colour code, which number does brown stand for?
27. 27.🧩 A capacitor in a circuit can … (a) make light (b) measure heat (c) spin a wheel (d) store charge briefly
28. 28.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it changes colour (d) it makes a sound
29. 29.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
30. 30.Which of these wastes electricity? (a) switch off empty rooms (b) leave the TV on standby (c) close the fridge quickly (d) use daylight to read
31. 31.📏 How many kilo-ohms (kΩ) is 7500 Ω? =
32. 32.True or false: on an LED, the leg by the flat edge is the anode (+). (a) False (b) True
33. 33.🌈 A resistor has the colour bands yellow, grey, yellow. What is its value in kilo-ohms (kΩ)? =
34. 34.⚡ A 0.6 W device works on 6 V. What current does it take (in amperes)? =
35. 35.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
36. 36.🧮 A 3.5 V battery is joined to 3 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
37. 37.📏 Which unit measures the flow of charge? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
38. 38.True or false: the flow of charge is measured in amperes (A). (a) True (b) False
39. 39.🔺 A current of 1.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔺 A 3 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =

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