Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 386 · 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 current of 0.25 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🧮 A 68 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
3. 3.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
4. 4.🧾 A 100 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
5. 5.⚡ A 9 W device works on 3 V. What current does it take (in amperes)? =
6. 6.🔍 Which is the odd one out? (a) leave the TV on standby (b) run fans in empty rooms (c) unplug idle chargers (d) use old filament bulbs
7. 7.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
8. 8.🧩 Which component senses how bright it is? (a) potentiometer (b) transistor (c) LDR (d) capacitor
9. 9.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to change its colour (d) to store charge
10. 10.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
11. 11.🧮 Resistors of 470 Ω, 47 Ω, 220 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
12. 12.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 volt (c) 1 watt (d) 1 ampere
13. 13.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
14. 14.🔺 A current of 0.2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
15. 15.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the length of a wire (d) the colour of light
16. 16.🌈 In the resistor colour code, which number does orange stand for?
17. 17.🧮 A 220 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
18. 18.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 25 % (d) 5 %
19. 19.🔺 A current of 10 mA flows when 1.5 V is joined across a resistor. What is its resistance (in ohms)?
20. 20.True or false: an LDR turns a fan or wheels. (a) False (b) True
21. 21.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) make light (d) store charge briefly
22. 22.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
23. 23.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
24. 24.🔺 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
25. 25.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it changes colour (c) it does not light (d) it lights brighter
26. 26.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = V ÷ I (d) R = I ÷ V
27. 27.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
28. 28.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
29. 29.💡 Does it save or waste electricity to unplug idle chargers? (a) wastes electricity (b) saves electricity
30. 30.🌈 A resistor has the colour bands grey, black, orange. What is its value in kilo-ohms (kΩ)? =
31. 31.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) bigger (d) stay the same
32. 32.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
33. 33.True or false: a buzzer boosts a small signal. (a) False (b) True
34. 34.💡 What does LED stand for? (a) light energy dial (b) low energy device (c) light-emitting diode (d) large electric dial
35. 35.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
36. 36.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.🌈 A resistor has the colour bands yellow, violet, brown. What is its value (in ohms)?
38. 38.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
39. 39.⚡ A 7.5 W device works on 5 V. What current does it take (in amperes)? =
40. 40.🧩 Which component blows if current is high? (a) transistor (b) fuse (c) motor (d) buzzer

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