Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 586 · 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.🌈 In the resistor colour code, which number does black stand for?
2. 2.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
3. 3.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 10 (c) 100 (d) 1000
4. 4.📏 How many milliamperes (mA) is 2.13 A?
5. 5.🔺 A current of 40 mA flows when 4.8 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
7. 7.Which of these wastes electricity? (a) switch off empty rooms (b) close the fridge quickly (c) set the AC to 24 °C (d) run fans in empty rooms
8. 8.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
9. 9.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
10. 10.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a filament bulb (d) a candle
11. 11.True or false: to run fans in empty rooms saves electricity. (a) False (b) True
12. 12.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.True or false: a resistor has coloured bands. (a) True (b) False
14. 14.What does a thermistor do? (a) senses how hot it is (b) has coloured bands (c) lets current go one way (d) senses how bright it is
15. 15.🌈 A resistor has the colour bands red, brown, black. What is its value (in ohms)?
16. 16.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
17. 17.🔍 Which is the odd one out? (a) use old filament bulbs (b) set the AC to 24 °C (c) iron one shirt at a time (d) run fans in empty rooms
18. 18.⚡ A 1.5 W device works on 3 V. What current does it take (in amperes)? =
19. 19.⚡ A 3 W device works on 6 V. What current does it take (in amperes)? =
20. 20.🧩 Which component glows using little power? (a) capacitor (b) transistor (c) LED (d) LDR
21. 21.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
22. 22.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V + I (d) P = V × I
23. 23.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
24. 24.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
26. 26.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
27. 27.True or false: energy used each second is measured in watts (W). (a) False (b) True
28. 28.📏 How many watts (W) is 2.9 kW?
29. 29.🧾 A 250 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
30. 30.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
31. 31.🔺 A current of 2.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.🧩 Which component senses how hot it is? (a) thermistor (b) LED (c) diode (d) fuse
33. 33.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
34. 34.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
35. 35.🔺 A current of 1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🧮 Resistors of 220 Ω, 10 Ω, 10 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
37. 37.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
38. 38.🧩 Which part changes electrical energy into movement? (a) a motor (b) an LED (c) a resistor (d) a fuse
39. 39.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the pipe colour (c) the tap handle (d) the water tank lid
40. 40.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =

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