Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 875 · 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 current of 2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
2. 2.What does a potentiometer do? (a) stores a little charge (b) is a resistance knob (c) senses how hot it is (d) lets current go one way
3. 3.Which of these is measured in volts (V)? (a) resistance (b) the flow of charge (c) the push of a cell (d) energy used each second
4. 4.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
5. 5.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 volt
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.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) the flow of water (c) the pipe colour (d) a narrow pipe
8. 8.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
9. 9.⚡ An 18 W device works on 12 V. What current does it take (in amperes)? =
10. 10.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
11. 11.🔺 A current of 10 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.📏 How many watts (W) is 2.8 kW?
13. 13.💡 A red LED uses 2 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
14. 14.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to make it brighter (d) to store charge
15. 15.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
16. 16.True or false: to set the AC to 24 °C saves electricity. (a) True (b) False
17. 17.What does a diode do? (a) stores a little charge (b) lets current go one way (c) has coloured bands (d) senses how bright it is
18. 18.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
19. 19.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) any band (d) the one nearest an end
20. 20.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)
21. 21.True or false: power is measured in watts (W). (a) True (b) False
22. 22.True or false: a resistor has coloured bands. (a) False (b) True
23. 23.⚡ A device works on 6 V and takes 0.2 A. What is its power (in watts)? =
24. 24.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
25. 25.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) energy used each second (d) the colour of light
26. 26.What does a transistor do? (a) lets current go one way (b) stores a little charge (c) has coloured bands (d) boosts a small signal
27. 27.Which of these wastes electricity? (a) iron one shirt at a time (b) use LED lamps (c) unplug idle chargers (d) switch off empty rooms
28. 28.Which of these saves electricity? (a) use old filament bulbs (b) leave fridge door open (c) set the AC to 24 °C (d) run fans in empty rooms
29. 29.🔺 A 30 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
30. 30.🌈 A resistor has the colour bands violet, green, red. What is its value in kilo-ohms (kΩ)? =
31. 31.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I + R (c) V = I ÷ R (d) V = I × R
32. 32.🧾 A 500 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
33. 33.🌈 In the resistor colour code, which number does violet stand for?
34. 34.⚡ A device works on 5 V and takes 0.1 A. What is its power (in watts)? =
35. 35.🔺 A current of 0.25 A flows when 1.25 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
37. 37.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 140 Ω resistor? (a) yellow-brown-brown (b) brown-yellow-brown (c) brown-yellow-black (d) brown-yellow-red
40. 40.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity

Free electronics lessons, practice and worksheets at talentjr.in/electronics-for-kids