Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 921 · 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 10 mA flows when 3.3 V is joined across a resistor. What is its resistance (in ohms)?
2. 2.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
4. 4.🧩 Which component lets current go one way? (a) LED (b) diode (c) capacitor (d) LDR
5. 5.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
6. 6.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
7. 7.🔺 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
8. 8.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V × I (c) R = V + I (d) R = V ÷ I
9. 9.True or false: an LDR has coloured bands. (a) False (b) True
10. 10.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
11. 11.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
12. 12.True or false: the voltmeter measures voltage. (a) True (b) False
13. 13.🧮 A 68 Ω resistor is joined in series with two equal 200 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
14. 14.🔺 A current of 25 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.True or false: the voltmeter measures current. (a) True (b) False
16. 16.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
17. 17.🧮 Two equal 220 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.🔺 A current of 1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
19. 19.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a resistor (d) a motor
20. 20.💡 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)?
21. 21.🔺 A current of 0.1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
22. 22.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) gets smaller (c) becomes zero (d) stays the same
23. 23.Which of these is measured in volts (V)? (a) power (b) how much a part resists (c) the push of a cell (d) the flow of charge
24. 24.📏 How many kilowatts (kW) is 4050 W? =
25. 25.True or false: a potentiometer lets current go one way. (a) True (b) False
26. 26.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 81000 Ω resistor? (a) brown-grey-orange (b) grey-brown-red (c) grey-brown-orange (d) grey-brown-yellow
27. 27.💡 An LED is joined to a 6 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) does not light (c) lights up
28. 28.🌈 In the resistor colour code, which number does blue stand for?
29. 29.📏 Which unit measures power? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)
30. 30.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) more than either one (d) less than either one
31. 31.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
32. 32.🧾 A 50 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
33. 33.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) stay the same (d) smaller
34. 34.⚡ A device works on 24 V and takes 0.1 A. What is its power (in watts)? =
35. 35.True or false: the voltmeter is joined across a part. (a) True (b) False
36. 36.Which of these wastes electricity? (a) unplug idle chargers (b) use LED lamps (c) leave fridge door open (d) use daylight to read
37. 37.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the water tank lid (c) the tap handle (d) the pipe colour
38. 38.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
39. 39.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an LED lamp (c) a candle (d) an oil lamp
40. 40.🔺 A 1 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =

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