Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 5 · 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 home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
2. 2.🧩 Which component is a resistance knob? (a) LDR (b) potentiometer (c) buzzer (d) motor
3. 3.🧩 Which component stores a little charge? (a) buzzer (b) transistor (c) capacitor (d) thermistor
4. 4.🔺 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
5. 5.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) gets bigger (c) becomes zero (d) stays the same
6. 6.🔺 An 8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
7. 7.🧮 A 2.6 V battery is joined to 10 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
8. 8.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) any band (d) the widest gap
9. 9.🔍 Which is the odd one out? (a) unplug idle chargers (b) use old filament bulbs (c) leave the TV on standby (d) run fans in empty rooms
10. 10.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to change its colour (d) to limit the current
11. 11.🧮 Resistors of 220 Ω, 20 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
12. 12.True or false: resistance is measured in amperes (A). (a) True (b) False
13. 13.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
14. 14.📏 How many kilowatts (kW) is 2750 W? =
15. 15.⚡ A 2.4 W device works on 24 V. What current does it take (in amperes)? =
16. 16.🧮 Resistors of 20 Ω, 47 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
17. 17.🧩 A capacitor in a circuit can … (a) store charge briefly (b) measure heat (c) spin a wheel (d) make light
18. 18.Which of these wastes electricity? (a) set the AC to 24 °C (b) use daylight to read (c) leave fridge door open (d) unplug idle chargers
19. 19.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
20. 20.🔺 A current of 1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🔺 A 12 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
22. 22.📏 How many milliamperes (mA) is 0.85 A?
23. 23.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
24. 24.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 50 % (c) 25 % (d) 5 %
25. 25.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
26. 26.⚡ A device works on 24 V and takes 1.5 A. What is its power (in watts)? =
27. 27.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
28. 28.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
29. 29.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🌈 A resistor has the colour bands brown, grey, black. What is its value (in ohms)?
31. 31.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 kilowatt-hour (kWh) (c) 1 volt (d) 1 ampere
33. 33.🔺 A current of 0.2 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.True or false: current is measured in watts (W). (a) False (b) True
35. 35.Which of these is measured in volts (V)? (a) resistance (b) current (c) the push of a cell (d) how much a part resists
36. 36.🔺 A current of 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 91000 Ω resistor? (a) brown-white-orange (b) white-brown-red (c) white-brown-orange (d) white-brown-yellow
38. 38.What does a buzzer do? (a) beeps for an alarm (b) blows if current is high (c) limits the current (d) lets current go one way
39. 39.🌈 A resistor has the colour bands red, yellow, red. What is its value in kilo-ohms (kΩ)? =
40. 40.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a resistor (d) a motor

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