Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 199 · 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.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
2. 2.What does a buzzer do? (a) makes a beeping sound (b) senses how hot it is (c) stores a little charge (d) limits the current
3. 3.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) a bigger tank (c) the flow of water (d) a narrow pipe
4. 4.Which of these is measured in amperes (A)? (a) power (b) the push of a cell (c) voltage (d) the flow of charge
5. 5.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
6. 6.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it does not light (c) it makes a sound (d) it lights brighter
7. 7.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
8. 8.True or false: an LDR stores a little charge. (a) True (b) False
9. 9.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
10. 10.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 volt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
11. 11.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
12. 12.💡 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)?
13. 13.🌈 A resistor has the colour bands yellow, grey, yellow. What is its value in kilo-ohms (kΩ)? =
14. 14.True or false: voltage is measured in volts (V). (a) True (b) False
15. 15.🌈 A resistor has the colour bands red, red, red. What is its value in kilo-ohms (kΩ)? =
16. 16.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 0 % (d) 25 %
17. 17.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
18. 18.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the pipe colour (c) the water pressure (d) the water tank lid
19. 19.🌈 A resistor has the colour bands red, grey, orange. What is its value in kilo-ohms (kΩ)? =
20. 20.True or false: the voltmeter measures current. (a) True (b) False
21. 21.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
22. 22.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
24. 24.Which of these is measured in volts (V)? (a) the flow of charge (b) the push of a cell (c) current (d) energy used each second
25. 25.🔺 A current of 0.5 A flows when 1.5 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
27. 27.Which of these is measured in watts (W)? (a) current (b) resistance (c) the flow of charge (d) energy used each second
28. 28.🔺 A current of 2.5 A flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
29. 29.🔺 A current of 50 mA flows when 16.5 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.🔺 A 7.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
31. 31.True or false: the ammeter measures voltage. (a) False (b) True
32. 32.Which of these is measured in ohms (Ω)? (a) current (b) how much a part resists (c) power (d) the flow of charge
33. 33.🔍 Which is the odd one out? (a) use old filament bulbs (b) unplug idle chargers (c) run fans in empty rooms (d) leave fridge door open
34. 34.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
35. 35.Which of these saves electricity? (a) leave the TV on standby (b) switch off empty rooms (c) use old filament bulbs (d) leave fridge door open
36. 36.📏 How many watts (W) is 4 kW?
37. 37.⚡ A device works on 3 V and takes 0.5 A. What is its power (in watts)? =
38. 38.🧩 Which component blows if current is high? (a) transistor (b) fuse (c) LED (d) buzzer
39. 39.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
40. 40.🧩 Which component smooths a wobbly supply? (a) capacitor (b) potentiometer (c) LED (d) thermistor

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