Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 115 · 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.What does a resistor do? (a) boosts a small signal (b) limits the current (c) lets current go one way (d) is a resistance knob
2. 2.True or false: the voltmeter is joined across a part. (a) True (b) False
3. 3.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) less than either one (d) more than either one
4. 4.⚡ A device works on 3 V and takes 0.1 A. What is its power (in watts)? =
5. 5.🧾 A 500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
6. 6.🔺 A current of 2.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a resistor (d) a motor
8. 8.🔺 A current of 0.1 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.🔍 Which is the odd one out? (a) iron one shirt at a time (b) use old filament bulbs (c) leave fridge door open (d) close the fridge quickly
10. 10.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
11. 11.⚡ A 0.5 W device works on 5 V. What current does it take (in amperes)? =
12. 12.🔍 Which is the odd one out? (a) unplug idle chargers (b) use daylight to read (c) leave the TV on standby (d) close the fridge quickly
13. 13.Which of these is measured in watts (W)? (a) how much a part resists (b) resistance (c) current (d) power
14. 14.🔺 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
15. 15.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
16. 16.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
17. 17.🧮 Resistors of 68 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
18. 18.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
19. 19.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) any band (d) the one nearest an end
20. 20.What does a thermistor do? (a) turns a fan or wheels (b) smooths a wobbly supply (c) makes a beeping sound (d) senses how hot it is
21. 21.💡 Why does an LED need a resistor in series? (a) to store charge (b) to limit the current (c) to make it brighter (d) to change its colour
22. 22.True or false: the voltmeter measures voltage. (a) False (b) True
23. 23.True or false: a thermistor senses how hot it is. (a) False (b) True
24. 24.⚡ A device works on 5 V and takes 1 A. What is its power (in watts)? =
25. 25.🧮 Resistors of 330 Ω, 20 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
26. 26.True or false: a capacitor smooths a wobbly supply. (a) False (b) True
27. 27.What does a fuse do? (a) stores a little charge (b) blows if current is high (c) smooths a wobbly supply (d) turns a fan or wheels
28. 28.💡 An LED is joined to a 9 V battery through a 470 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) does not light (c) lights up
29. 29.🔺 A current of 3 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🔺 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
31. 31.🔺 A 10 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
32. 32.📏 How many kilowatts (kW) is 250 W? =
33. 33.True or false: to use old filament bulbs wastes electricity. (a) True (b) False
34. 34.🌈 In the resistor colour code, which number does green stand for?
35. 35.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 ampere (c) 1 volt (d) 1 watt
36. 36.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 95000 Ω resistor? (a) white-green-red (b) white-green-orange (c) green-white-orange (d) white-green-yellow
37. 37.🌈 A resistor has the colour bands red, white, red. What is its value in kilo-ohms (kΩ)? =
38. 38.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
39. 39.🧾 A 1000 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
40. 40.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

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