Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 433 · 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 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
2. 2.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to limit the current (d) to store charge
3. 3.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the length of a wire (d) the size of a cell
4. 4.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
5. 5.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🔺 A current of 2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🔺 A 7.5 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
8. 8.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
9. 9.📏 Which unit measures voltage? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)
10. 10.🔺 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
11. 11.🔺 A current of 2.5 A flows when 25 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.🔺 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
13. 13.What does a diode do? (a) has coloured bands (b) boosts a small signal (c) lets current go one way (d) limits the current
14. 14.🧮 Resistors of 22 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
15. 15.True or false: a capacitor smooths a wobbly supply. (a) False (b) True
16. 16.📏 Which unit measures energy used each second? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
17. 17.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
18. 18.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 60 (c) 1000 (d) 100
19. 19.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
20. 20.💡 An LED is joined to a 6 V battery through a 220 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
21. 21.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
22. 22.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
23. 23.🔺 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
24. 24.🔺 A current of 1.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) their sum (d) always zero
26. 26.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
27. 27.🔺 An 8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
28. 28.Which of these saves electricity? (a) leave fridge door open (b) iron one shirt at a time (c) use daylight to read (d) use old filament bulbs
29. 29.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
30. 30.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 0 % (c) 50 % (d) 5 %
31. 31.🔺 A current of 10 mA flows when 1.5 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.🧩 Which component limits the current? (a) LED (b) resistor (c) potentiometer (d) thermistor
33. 33.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 690 Ω resistor? (a) blue-white-red (b) blue-white-black (c) white-blue-brown (d) blue-white-brown
34. 34.True or false: a fuse senses how hot it is. (a) True (b) False
35. 35.📏 How many watts (W) is 3.7 kW?
36. 36.True or false: the push of a cell is measured in amperes (A). (a) False (b) True
37. 37.What does a motor do? (a) has coloured bands (b) stores a little charge (c) lets current go one way (d) makes things spin
38. 38.🔺 A 3.75 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
39. 39.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
40. 40.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 4 V supply. What current flows (in mA)?

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