Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 67 · 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.What does a fuse do? (a) blows if current is high (b) is a resistance knob (c) limits the current (d) beeps for an alarm
2. 2.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water tank lid (c) the water pressure (d) the pipe colour
3. 3.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
4. 4.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 10 (d) 1000
5. 5.True or false: the voltmeter is joined across a part. (a) True (b) False
6. 6.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
7. 7.🔺 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
8. 8.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
9. 9.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
10. 10.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
11. 11.True or false: the ammeter measures voltage. (a) False (b) True
12. 12.🔺 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
13. 13.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a capacitor (d) a diode
14. 14.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
15. 15.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
16. 16.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
17. 17.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
18. 18.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
19. 19.True or false: a buzzer makes a beeping sound. (a) False (b) True
20. 20.🌈 Which band is read first on a resistor? (a) any band (b) the gold band (c) the widest gap (d) the one nearest an end
21. 21.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🌈 In the resistor colour code, which number does green stand for?
23. 23.📏 Which unit measures how much a part resists? (a) watt (W) (b) ampere (A) (c) volt (V) (d) ohm (Ω)
24. 24.🌈 In the resistor colour code, which number does yellow stand for?
25. 25.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
26. 26.📏 How many ohms (Ω) is 5.7 kΩ?
27. 27.💡 An LED is joined to a 9 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) lights up (c) may burn out
28. 28.📏 How many amperes (A) is 1200 mA? =
29. 29.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) the size of a cell (d) energy used each second
30. 30.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🧩 Which component smooths a wobbly supply? (a) buzzer (b) thermistor (c) resistor (d) capacitor
33. 33.⚡ A 4.5 W device works on 1.5 V. What current does it take (in amperes)? =
34. 34.What does a transistor do? (a) boosts a small signal (b) senses how bright it is (c) has coloured bands (d) smooths a wobbly supply
35. 35.🧩 Which component is a resistance knob? (a) LDR (b) fuse (c) potentiometer (d) capacitor
36. 36.True or false: the push of a cell is measured in ohms (Ω). (a) False (b) True
37. 37.🔺 A current of 20 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.⚡ A device works on 3 V and takes 1.5 A. What is its power (in watts)? =
39. 39.🧾 A 1000 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
40. 40.🔺 A current of 0.25 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =

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