Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 643 · 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.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to make it brighter (d) to limit the current
2. 2.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
3. 3.💡 What does LED stand for? (a) light energy dial (b) light-emitting diode (c) low energy device (d) large electric dial
4. 4.What does a buzzer do? (a) beeps for an alarm (b) stores a little charge (c) has coloured bands (d) glows using little power
5. 5.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I × R (c) V = I ÷ R (d) V = I + R
6. 6.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 watt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
7. 7.🧮 A 3.5 V battery is joined to 5 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
8. 8.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
9. 9.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) smaller (d) zero
10. 10.Which of these is measured in watts (W)? (a) resistance (b) current (c) how much a part resists (d) energy used each second
11. 11.🧾 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?
12. 12.📏 In the water-pipe picture of a circuit, current is like … (a) the flow of water (b) a narrow pipe (c) the pipe colour (d) the water pressure
13. 13.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) stays the same (d) gets bigger
15. 15.Which of these is measured in volts (V)? (a) current (b) resistance (c) voltage (d) how much a part resists
16. 16.True or false: a potentiometer blows if current is high. (a) False (b) True
17. 17.Which of these saves electricity? (a) iron one shirt at a time (b) run fans in empty rooms (c) set the AC to 24 °C (d) use old filament bulbs
18. 18.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
19. 19.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
20. 20.⚡ A device works on 3 V and takes 0.2 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 = V ÷ I (d) R = I ÷ V
22. 22.True or false: an LDR lets current go one way. (a) True (b) False
23. 23.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
25. 25.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
26. 26.🔺 A 6.25 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
27. 27.🧮 A 22 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)?
28. 28.What does a fuse do? (a) blows if current is high (b) turns a fan or wheels (c) makes things spin (d) limits the current
29. 29.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
30. 30.🧮 Resistors of 10 Ω, 100 Ω, 33 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
31. 31.🔺 A 40 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
32. 32.True or false: the voltmeter measures current. (a) True (b) False
33. 33.🧾 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
34. 34.True or false: to unplug idle chargers saves electricity. (a) False (b) True
35. 35.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) always zero (d) less than either one
37. 37.Which of these is measured in volts (V)? (a) energy used each second (b) the push of a cell (c) resistance (d) the flow of charge
38. 38.True or false: a resistor has coloured bands. (a) False (b) True
39. 39.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
40. 40.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?

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