Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 98 · 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.True or false: to close the fridge quickly wastes electricity. (a) False (b) True
2. 2.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V × I (c) R = V ÷ I (d) R = I ÷ V
3. 3.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = R ÷ I (d) V = I × R
4. 4.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the size of a cell (d) the colour of light
5. 5.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
6. 6.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
7. 7.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to limit the current (d) to change its colour
8. 8.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) gets bigger (d) stays the same
9. 9.🌈 A resistor has the colour bands white, violet, black. What is its value (in ohms)?
10. 10.🌈 A resistor has the colour bands green, orange, orange. What is its value (in ohms)?
11. 11.Which of these wastes electricity? (a) leave fridge door open (b) unplug idle chargers (c) switch off empty rooms (d) use daylight to read
12. 12.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🧾 A 500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
14. 14.🌈 In the resistor colour code, which number does red stand for?
15. 15.Which of these is measured in amperes (A)? (a) voltage (b) resistance (c) the push of a cell (d) current
16. 16.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
17. 17.🔺 A 20 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
18. 18.True or false: voltage is measured in ohms (Ω). (a) False (b) True
19. 19.🔺 A current of 0.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
20. 20.🔺 A current of 1 A flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.True or false: to use LED lamps wastes electricity. (a) False (b) True
22. 22.🧮 A 330 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)?
23. 23.True or false: power is measured in watts (W). (a) True (b) False
24. 24.🧩 Which component glows using little power? (a) thermistor (b) LDR (c) LED (d) diode
25. 25.🌈 In the resistor colour code, which number does green stand for?
26. 26.⚡ A device works on 9 V and takes 0.25 A. What is its power (in watts)? =
27. 27.True or false: a capacitor limits the current. (a) True (b) False
28. 28.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = R ÷ V (c) I = V + R (d) I = V × R
29. 29.📏 How many milliamperes (mA) is 0.72 A?
30. 30.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
31. 31.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water tank lid (b) the tap handle (c) the pipe colour (d) the water pressure
32. 32.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) store charge briefly (d) make light
34. 34.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
35. 35.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 10 (d) 1000
36. 36.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.Which of these wastes electricity? (a) close the fridge quickly (b) use LED lamps (c) use old filament bulbs (d) unplug idle chargers
38. 38.🔺 A current of 10 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
39. 39.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
40. 40.🧮 Two equal 220 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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