Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 701 · 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 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
2. 2.What does a transistor do? (a) boosts a small signal (b) has coloured bands (c) makes things spin (d) glows using little power
3. 3.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it does not light (d) it changes colour
4. 4.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
5. 5.🧩 Which component glows using little power? (a) LDR (b) LED (c) potentiometer (d) thermistor
6. 6.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
7. 7.Which of these is measured in amperes (A)? (a) current (b) voltage (c) energy used each second (d) the push of a cell
8. 8.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
9. 9.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
10. 10.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = R ÷ I (c) V = I + R (d) V = I ÷ R
11. 11.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the tap handle (c) the pipe colour (d) the water tank lid
12. 12.Which of these saves electricity? (a) run fans in empty rooms (b) iron one shirt at a time (c) use LED lamps (d) use old filament bulbs
13. 13.Which of these saves electricity? (a) leave the TV on standby (b) leave fridge door open (c) use old filament bulbs (d) unplug idle chargers
14. 14.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) stays the same (c) becomes zero (d) gets bigger
15. 15.Which of these is measured in volts (V)? (a) current (b) the push of a cell (c) energy used each second (d) how much a part resists
16. 16.True or false: a thermistor senses how hot it is. (a) True (b) False
17. 17.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 volt (c) 1 kilowatt-hour (kWh) (d) 1 watt
18. 18.Which of these wastes electricity? (a) set the AC to 24 °C (b) leave the TV on standby (c) use daylight to read (d) unplug idle chargers
19. 19.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
20. 20.🧮 A 10 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
21. 21.🧮 Resistors of 68 Ω, 150 Ω, 220 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
22. 22.🧮 A 470 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
23. 23.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = V × R (c) I = R ÷ V (d) I = V ÷ R
24. 24.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
25. 25.True or false: an LDR smooths a wobbly supply. (a) False (b) True
26. 26.📏 How many amperes (A) is 2900 mA? =
27. 27.True or false: to use daylight to read wastes electricity. (a) True (b) False
28. 28.True or false: the push of a cell is measured in volts (V). (a) True (b) False
29. 29.True or false: resistance is measured in watts (W). (a) False (b) True
30. 30.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
31. 31.True or false: to set the AC to 24 °C saves electricity. (a) False (b) True
32. 32.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🔺 A 60 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
34. 34.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
35. 35.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 8400 Ω resistor? (a) grey-yellow-red (b) grey-yellow-orange (c) yellow-grey-red (d) grey-yellow-brown
36. 36.🌈 In the resistor colour code, which number does black stand for?
37. 37.🧮 A 33 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
38. 38.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.📏 Which unit measures power? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
40. 40.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =

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