Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 653 · 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 0.5 A flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
2. 2.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
3. 3.🔺 A current of 0.1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the widest gap (d) the gold band
5. 5.🧮 Resistors of 33 Ω, 330 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.💡 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)?
7. 7.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
8. 8.True or false: the flow of charge is measured in volts (V). (a) False (b) True
9. 9.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) use LED lamps (c) unplug idle chargers (d) use old filament bulbs
10. 10.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
11. 11.📏 How many watts (W) is 4.4 kW?
12. 12.True or false: the ammeter is joined in series. (a) False (b) True
13. 13.True or false: a fuse senses how bright it is. (a) True (b) False
14. 14.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V ÷ R (c) I = V × R (d) I = V + R
15. 15.📏 How many kilo-ohms (kΩ) is 200 Ω? =
16. 16.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V × I (d) P = V + I
17. 17.True or false: a potentiometer is a resistance knob. (a) True (b) False
18. 18.True or false: a transistor boosts a small signal. (a) False (b) True
19. 19.True or false: the ammeter is joined across a part. (a) False (b) True
20. 20.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
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.🧾 A 500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
23. 23.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 60 (d) 1000
24. 24.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
25. 25.🌈 A resistor has the colour bands orange, white, red. What is its value in kilo-ohms (kΩ)? =
26. 26.📏 How many ohms (Ω) is 4.3 kΩ?
27. 27.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
28. 28.🔺 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
29. 29.True or false: the voltmeter is joined across a part. (a) True (b) False
30. 30.🔺 A 22.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
31. 31.🌈 In the resistor colour code, which number does green stand for?
32. 32.🧮 Resistors of 22 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
33. 33.💡 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
34. 34.🧩 Which component turns a fan or wheels? (a) motor (b) LDR (c) capacitor (d) resistor
35. 35.Which of these saves electricity? (a) leave the TV on standby (b) run fans in empty rooms (c) leave fridge door open (d) use daylight to read
36. 36.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
37. 37.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
38. 38.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
39. 39.🌈 A resistor has the colour bands blue, orange, orange. What is its value (in ohms)?
40. 40.🧮 A 7.5 V battery is joined to 3 Ω and 12 Ω resistors in series. What current flows (in amperes)? =

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