Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 923 · 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.🌈 In the resistor colour code, which number does brown stand for?
2. 2.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
3. 3.True or false: the ammeter measures current. (a) False (b) True
4. 4.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
5. 5.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
6. 6.⚡ A device works on 6 V and takes 3 A. What is its power (in watts)? =
7. 7.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
8. 8.🧩 Which component boosts a small signal? (a) thermistor (b) motor (c) buzzer (d) transistor
9. 9.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
10. 10.🧩 Which component blows if current is high? (a) potentiometer (b) transistor (c) fuse (d) LDR
11. 11.🌈 A resistor has the colour bands orange, white, red. What is its value in kilo-ohms (kΩ)? =
12. 12.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
13. 13.True or false: resistance is measured in ohms (Ω). (a) False (b) True
14. 14.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 54000 Ω resistor? (a) green-yellow-orange (b) green-yellow-red (c) green-yellow-yellow (d) yellow-green-orange
15. 15.🧮 Resistors of 470 Ω, 100 Ω, 33 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
16. 16.True or false: the voltmeter is joined in series. (a) False (b) True
17. 17.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
19. 19.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
20. 20.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1000 (b) 1024 (c) 10 (d) 100
21. 21.📏 Which unit measures the push of a cell? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
22. 22.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to make it brighter (d) to store charge
23. 23.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
24. 24.📏 Which unit measures energy used each second? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
25. 25.🌈 A resistor has the colour bands violet, blue, black. What is its value (in ohms)?
26. 26.True or false: a transistor boosts a small signal. (a) True (b) False
27. 27.🔺 A 12 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
28. 28.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
29. 29.⚡ A 1 W device works on 5 V. What current does it take (in amperes)? =
30. 30.🧩 A capacitor in a circuit can … (a) measure heat (b) store charge briefly (c) make light (d) spin a wheel
31. 31.🔺 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
32. 32.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) bigger (d) smaller
33. 33.True or false: a diode glows using little power. (a) True (b) False
34. 34.🧮 A 100 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
35. 35.🔺 A current of 0.25 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
36. 36.True or false: to use daylight to read wastes electricity. (a) True (b) False
37. 37.⚡ A 9 W device works on 3 V. What current does it take (in amperes)? =
38. 38.🧮 Four equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.🧩 Which component lets current go one way? (a) capacitor (b) buzzer (c) LED (d) diode
40. 40.🧩 Which component is a resistance knob? (a) fuse (b) diode (c) potentiometer (d) capacitor

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