Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 634 · 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.💡 Does it save or waste electricity to use old filament bulbs? (a) saves electricity (b) wastes electricity
2. 2.🔺 A current of 50 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🔺 A 10 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
4. 4.⚡ A device works on 12 V and takes 3 A. What is its power (in watts)? =
5. 5.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
6. 6.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🌈 A resistor has the colour bands blue, green, orange. What is its value (in ohms)?
8. 8.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
9. 9.True or false: a potentiometer is a resistance knob. (a) False (b) True
10. 10.🔺 A 12 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
11. 11.True or false: to iron one shirt at a time saves electricity. (a) False (b) True
12. 12.⚡ Power tells us … (a) energy used each second (b) the colour of light (c) the length of a wire (d) the size of a cell
13. 13.🔺 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
14. 14.📏 Which unit measures the push of a cell? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
15. 15.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
16. 16.🔍 Which is the odd one out? (a) use old filament bulbs (b) leave the TV on standby (c) leave fridge door open (d) use LED lamps
17. 17.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) spin a wheel (d) measure heat
18. 18.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
19. 19.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
20. 20.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.💡 Does it save or waste electricity to close the fridge quickly? (a) saves electricity (b) wastes electricity
22. 22.True or false: the ammeter is joined across a part. (a) True (b) False
23. 23.True or false: a buzzer beeps for an alarm. (a) False (b) True
24. 24.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
25. 25.🔺 A current of 1.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
26. 26.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
27. 27.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
28. 28.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
29. 29.🌈 A resistor has the colour bands white, black, red. What is its value (in ohms)?
30. 30.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
31. 31.What does a diode do? (a) has coloured bands (b) turns a fan or wheels (c) lets current go one way (d) limits the current
32. 32.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) any band (d) the gold band
33. 33.💡 A red LED uses 2 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
34. 34.🔺 A current of 25 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
36. 36.🔺 A current of 0.25 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
39. 39.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
40. 40.🔺 A current of 2.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =

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