Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 284 · 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.🔺 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
2. 2.Which of these is measured in watts (W)? (a) voltage (b) the flow of charge (c) resistance (d) energy used each second
3. 3.What does a thermistor do? (a) turns a fan or wheels (b) senses how hot it is (c) glows using little power (d) beeps for an alarm
4. 4.True or false: a resistor smooths a wobbly supply. (a) True (b) False
5. 5.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
6. 6.⚡ A device works on 6 V and takes 3 A. What is its power (in watts)? =
7. 7.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an oil lamp (c) an LED lamp (d) a filament bulb
8. 8.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.🔺 A current of 2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
10. 10.🧮 A 4 V battery is joined to 12 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
11. 11.True or false: the voltmeter is joined across a part. (a) True (b) False
12. 12.True or false: the ammeter measures current. (a) False (b) True
13. 13.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V ÷ R (c) I = V × R (d) I = V + R
14. 14.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) energy used each second (d) the size of a cell
15. 15.🧩 A capacitor in a circuit can … (a) store charge briefly (b) make light (c) measure heat (d) spin a wheel
16. 16.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 25 % (d) 50 %
17. 17.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
18. 18.True or false: an LED beeps for an alarm. (a) True (b) False
19. 19.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 19 Ω resistor? (a) white-brown-black (b) brown-white-brown (c) brown-white-black (d) red-white-black
21. 21.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
22. 22.📏 Which unit measures voltage? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
23. 23.Which of these is measured in amperes (A)? (a) current (b) power (c) how much a part resists (d) resistance
24. 24.💡 Does it save or waste electricity to unplug idle chargers? (a) saves electricity (b) wastes electricity
25. 25.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to store charge (d) to change its colour
26. 26.Which of these saves electricity? (a) leave the TV on standby (b) unplug idle chargers (c) iron one shirt at a time (d) use old filament bulbs
27. 27.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
28. 28.True or false: the voltmeter measures voltage. (a) True (b) False
29. 29.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
30. 30.💡 An LED is joined to a 6 V battery through a 330 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) may burn out (b) lights up (c) does not light
31. 31.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🧩 Which component beeps for an alarm? (a) motor (b) buzzer (c) resistor (d) diode
33. 33.🌈 In the resistor colour code, which number does blue stand for?
34. 34.🔺 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
35. 35.True or false: to set the AC to 24 °C wastes electricity. (a) False (b) True
36. 36.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🌈 A resistor has the colour bands blue, grey, orange. What is its value in kilo-ohms (kΩ)? =
38. 38.🧾 A 500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
39. 39.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
40. 40.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter

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