Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 820 · 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.🔺 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
2. 2.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
3. 3.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
4. 4.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
5. 5.📏 How many ohms (Ω) is 1.7 kΩ?
6. 6.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it does not light (c) it makes a sound (d) it lights brighter
7. 7.True or false: a thermistor makes a beeping sound. (a) True (b) False
8. 8.🧾 A 100 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
9. 9.True or false: the voltmeter measures current. (a) False (b) True
10. 10.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
11. 11.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
12. 12.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
13. 13.🔺 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
14. 14.Which of these is measured in amperes (A)? (a) resistance (b) voltage (c) energy used each second (d) the flow of charge
15. 15.🔺 A 2.2 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.🔺 A 3.3 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
17. 17.🔺 A current of 0.5 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
18. 18.🔺 A current of 0.2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 75 Ω resistor? (a) violet-green-black (b) violet-green-brown (c) grey-green-black (d) green-violet-black
20. 20.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V × I (c) R = I ÷ V (d) R = V + I
21. 21.True or false: a fuse blows if current is high. (a) True (b) False
22. 22.True or false: to use daylight to read wastes electricity. (a) False (b) True
23. 23.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
24. 24.📏 Which unit measures current? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
25. 25.⚡ A 0.3 W device works on 3 V. What current does it take (in amperes)? =
26. 26.True or false: a capacitor senses how bright it is. (a) True (b) False
27. 27.True or false: how much a part resists is measured in ohms (Ω). (a) False (b) True
28. 28.True or false: a motor has coloured bands. (a) True (b) False
29. 29.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
30. 30.What does an LED do? (a) glows using little power (b) makes things spin (c) stores a little charge (d) lets current go one way
31. 31.What does a resistor do? (a) has coloured bands (b) beeps for an alarm (c) lets current go one way (d) blows if current is high
32. 32.⚡ A device works on 3 V and takes 1.5 A. What is its power (in watts)? =
33. 33.🌈 A resistor has the colour bands blue, red, yellow. What is its value in kilo-ohms (kΩ)? =
34. 34.💡 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?
35. 35.🧮 A 7 V battery is joined to 8 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
36. 36.🔺 A current of 2.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.Which of these saves electricity? (a) leave fridge door open (b) use daylight to read (c) leave the TV on standby (d) use old filament bulbs
40. 40.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V × I (d) P = V ÷ I

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