Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 526 · 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.True or false: to unplug idle chargers saves electricity. (a) True (b) False
2. 2.🔺 A 1.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
3. 3.🔺 A current of 1.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
4. 4.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
5. 5.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I × R (c) V = R ÷ I (d) V = I ÷ R
6. 6.True or false: a potentiometer is a resistance knob. (a) False (b) True
7. 7.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
8. 8.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
9. 9.🔺 A 25 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
10. 10.🌈 In the resistor colour code, which number does yellow stand for?
11. 11.🔺 A 20 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
12. 12.🌈 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
13. 13.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 25 % (c) 50 % (d) 0 %
14. 14.🔺 A current of 50 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 watt (c) 1 kilowatt-hour (kWh) (d) 1 ampere
16. 16.🧮 A 33 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
17. 17.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 10 (c) 1000 (d) 60
18. 18.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the size of a cell (d) the colour of light
19. 19.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it does not light (c) it changes colour (d) it lights brighter
20. 20.⚡ A device works on 1.5 V and takes 0.5 A. What is its power (in watts)? =
21. 21.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
22. 22.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
23. 23.What does a transistor do? (a) beeps for an alarm (b) boosts a small signal (c) glows using little power (d) turns a fan or wheels
24. 24.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
25. 25.⚡ A 2.25 W device works on 9 V. What current does it take (in amperes)? =
26. 26.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) use daylight to read (c) leave the TV on standby (d) use LED lamps
28. 28.🔍 Which is the odd one out? (a) unplug idle chargers (b) set the AC to 24 °C (c) close the fridge quickly (d) iron one shirt at a time
29. 29.True or false: the ammeter is joined across a part. (a) True (b) False
30. 30.💡 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?
31. 31.⚡ A 2.4 W device works on 24 V. What current does it take (in amperes)? =
32. 32.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets bigger (d) gets smaller
33. 33.⚡ An 18 W device works on 12 V. What current does it take (in amperes)? =
34. 34.🔍 Which is the odd one out? (a) leave fridge door open (b) unplug idle chargers (c) use old filament bulbs (d) iron one shirt at a time
35. 35.🧩 Which component senses how bright it is? (a) LDR (b) fuse (c) motor (d) thermistor
36. 36.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
37. 37.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
38. 38.🌈 A resistor has the colour bands violet, violet, brown. What is its value (in ohms)?
39. 39.🔺 A current of 0.25 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
40. 40.📏 Which unit measures resistance? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)

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