Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 54 · 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 0.2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
2. 2.True or false: to close the fridge quickly wastes electricity. (a) True (b) False
3. 3.🧮 Resistors of 220 Ω, 470 Ω, 150 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
4. 4.🌈 A resistor has the colour bands white, red, orange. What is its value (in ohms)?
5. 5.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
6. 6.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
7. 7.True or false: voltage is measured in amperes (A). (a) True (b) False
8. 8.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
9. 9.💡 Does it save or waste electricity to iron one shirt at a time? (a) saves electricity (b) wastes electricity
10. 10.🧩 Which component has coloured bands? (a) motor (b) LED (c) diode (d) resistor
11. 11.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
12. 12.Which of these saves electricity? (a) run fans in empty rooms (b) use LED lamps (c) iron one shirt at a time (d) leave fridge door open
13. 13.🔺 A 10 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
14. 14.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) use daylight to read (c) run fans in empty rooms (d) use LED lamps
15. 15.🔺 A current of 1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
16. 16.💡 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?
17. 17.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
18. 18.📏 Which unit measures resistance? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
19. 19.⚡ A 1.5 W device works on 3 V. What current does it take (in amperes)? =
20. 20.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
21. 21.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V × I (c) R = I ÷ V (d) R = V + I
22. 22.💡 Does it save or waste electricity to unplug idle chargers? (a) wastes electricity (b) saves electricity
23. 23.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) unplug idle chargers (c) use old filament bulbs (d) use LED lamps
24. 24.📏 Which unit measures power? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
25. 25.📏 How many watts (W) is 2.4 kW?
26. 26.📏 Which unit measures how much a part resists? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
27. 27.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) store charge briefly (d) measure heat
28. 28.True or false: a resistor limits the current. (a) False (b) True
29. 29.🧮 A 1.75 V battery is joined to 4 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
30. 30.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) the widest gap (d) any band
31. 31.Which of these is measured in volts (V)? (a) how much a part resists (b) the flow of charge (c) the push of a cell (d) resistance
32. 32.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) energy used each second (d) the size of a cell
33. 33.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = V × I (d) P = I ÷ V
34. 34.🔺 A current of 20 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
35. 35.True or false: to use LED lamps wastes electricity. (a) False (b) True
36. 36.💡 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?
37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 6600 Ω resistor? (a) blue-blue-red (b) blue-violet-red (c) blue-blue-brown (d) blue-blue-orange
38. 38.What does a thermistor do? (a) smooths a wobbly supply (b) turns a fan or wheels (c) blows if current is high (d) senses how hot it is
39. 39.🧮 A 20 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
40. 40.🧩 Which component turns a fan or wheels? (a) thermistor (b) motor (c) LDR (d) fuse

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