Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 677 · 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.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
2. 2.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
3. 3.🔺 A current of 40 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🔍 Which is the odd one out? (a) use daylight to read (b) switch off empty rooms (c) use LED lamps (d) leave fridge door open
5. 5.🌈 In the resistor colour code, which number does violet stand for?
6. 6.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a filament bulb (c) an oil lamp (d) a candle
7. 7.📏 How many amperes (A) is 1380 mA? =
8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 93 Ω resistor? (a) white-orange-brown (b) white-orange-black (c) brown-orange-black (d) orange-white-black
9. 9.⚡ 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
10. 10.🔺 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
11. 11.📏 Which unit measures the push of a cell? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
12. 12.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
13. 13.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
14. 14.🧮 A 2.25 V battery is joined to 4 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
15. 15.True or false: the push of a cell is measured in ohms (Ω). (a) True (b) False
16. 16.🔺 A 10 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
17. 17.True or false: energy used each second is measured in volts (V). (a) True (b) False
18. 18.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
19. 19.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
20. 20.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
21. 21.True or false: a resistor limits the current. (a) True (b) False
22. 22.🧾 A 200 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
23. 23.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it changes colour (c) it does not light (d) it makes a sound
24. 24.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
25. 25.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a resistor (d) a motor
26. 26.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
27. 27.⚡ Which formula gives electric power? (a) P = V × I (b) P = I ÷ V (c) P = V + I (d) P = V ÷ I
28. 28.🔺 A 5 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
29. 29.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) spin a wheel (d) measure heat
31. 31.🔍 Which is the odd one out? (a) leave the TV on standby (b) unplug idle chargers (c) iron one shirt at a time (d) use old filament bulbs
32. 32.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
33. 33.True or false: to switch off empty rooms saves electricity. (a) False (b) True
34. 34.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
35. 35.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets bigger (d) gets smaller
36. 36.True or false: to use LED lamps wastes electricity. (a) True (b) False
37. 37.True or false: a capacitor boosts a small signal. (a) False (b) True
38. 38.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
39. 39.🧮 Resistors of 470 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
40. 40.Which of these is measured in watts (W)? (a) voltage (b) current (c) power (d) how much a part resists

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