Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 408 · 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 1.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
2. 2.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
3. 3.Which of these saves electricity? (a) use old filament bulbs (b) run fans in empty rooms (c) use daylight to read (d) iron one shirt at a time
4. 4.⚡ A device works on 3 V and takes 1.5 A. What is its power (in watts)? =
5. 5.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
6. 6.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V ÷ R (c) I = V + R (d) I = R ÷ V
7. 7.True or false: an LDR has coloured bands. (a) True (b) False
8. 8.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) stays the same (d) gets bigger
10. 10.🧩 Which component makes things spin? (a) motor (b) LDR (c) fuse (d) potentiometer
11. 11.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) less than either one (d) their sum
12. 12.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
13. 13.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
14. 14.🔺 A current of 3 A flows when 60 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.🧮 Resistors of 150 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
16. 16.🌈 In the resistor colour code, which number does blue stand for?
17. 17.🌈 In the resistor colour code, which number does white stand for?
18. 18.🔺 A 2.5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
19. 19.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 700 Ω resistor? (a) violet-black-black (b) violet-black-red (c) grey-violet-brown (d) violet-black-brown
20. 20.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧩 Which part changes electrical energy into movement? (a) a motor (b) a fuse (c) a resistor (d) an LED
22. 22.🧮 A 5 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
23. 23.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
24. 24.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to make it brighter (d) to limit the current
25. 25.🧮 A 1.6 V battery is joined to 2 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
26. 26.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) store charge briefly (d) spin a wheel
27. 27.🧮 A 330 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
28. 28.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I × R (c) V = I + R (d) V = R ÷ I
29. 29.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
30. 30.🌈 In the resistor colour code, which number does orange stand for?
31. 31.🔺 A 5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
32. 32.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
33. 33.True or false: to use old filament bulbs saves electricity. (a) False (b) True
34. 34.🌈 A resistor has the colour bands green, red, brown. What is its value (in ohms)?
35. 35.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
36. 36.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
37. 37.📏 How many watts (W) is 2.9 kW?
38. 38.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an LED lamp (c) an oil lamp (d) a filament bulb
39. 39.True or false: energy used each second is measured in ohms (Ω). (a) True (b) False
40. 40.🧩 Which component beeps for an alarm? (a) transistor (b) potentiometer (c) LDR (d) buzzer

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