Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 280 · 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 red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
2. 2.📏 Which unit measures voltage? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
3. 3.💡 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
4. 4.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) stay the same (d) smaller
6. 6.🧩 Which component turns a fan or wheels? (a) motor (b) fuse (c) thermistor (d) diode
7. 7.🧮 Resistors of 22 Ω, 22 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
8. 8.Which of these is measured in volts (V)? (a) voltage (b) resistance (c) power (d) current
9. 9.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V ÷ I (c) R = V + I (d) R = V × I
10. 10.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a capacitor (d) a resistor
11. 11.🧾 A 2000 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
12. 12.True or false: the voltmeter measures current. (a) False (b) True
13. 13.🧮 A 50 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)?
14. 14.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 5900 Ω resistor? (a) green-white-red (b) white-green-red (c) green-white-orange (d) green-white-brown
15. 15.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
16. 16.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
17. 17.Which of these is measured in amperes (A)? (a) the flow of charge (b) energy used each second (c) how much a part resists (d) resistance
18. 18.🔺 A current of 1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
19. 19.💡 What does LED stand for? (a) low energy device (b) large electric dial (c) light energy dial (d) light-emitting diode
20. 20.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
21. 21.🌈 A resistor has the colour bands brown, green, black. What is its value (in ohms)?
22. 22.🔺 A current of 20 mA flows when 9.4 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.What does an LDR do? (a) has coloured bands (b) senses how bright it is (c) boosts a small signal (d) makes things spin
24. 24.🔺 A 4 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
25. 25.🌈 In the resistor colour code, which number does red stand for?
26. 26.🔺 A current of 1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🧩 Which component boosts a small signal? (a) diode (b) LDR (c) thermistor (d) transistor
28. 28.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V ÷ I (d) P = V × I
29. 29.🔺 A current of 3 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
30. 30.True or false: the ammeter measures current. (a) False (b) True
31. 31.🔺 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
32. 32.🔍 Which is the odd one out? (a) use LED lamps (b) use old filament bulbs (c) close the fridge quickly (d) set the AC to 24 °C
33. 33.True or false: the push of a cell is measured in amperes (A). (a) False (b) True
34. 34.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
35. 35.🔺 A current of 1.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
37. 37.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 volt
40. 40.🧮 Resistors of 22 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?

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