Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 287 · 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 motor do? (a) boosts a small signal (b) makes things spin (c) makes a beeping sound (d) senses how hot it is
2. 2.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
3. 3.🧩 Which part changes electrical energy into movement? (a) a motor (b) a fuse (c) an LED (d) a resistor
4. 4.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
5. 5.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
6. 6.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
7. 7.🌈 A resistor has the colour bands green, violet, orange. What is its value in kilo-ohms (kΩ)? =
8. 8.What does a transistor do? (a) boosts a small signal (b) turns a fan or wheels (c) glows using little power (d) limits the current
9. 9.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
10. 10.🌈 In the resistor colour code, which number does orange stand for?
11. 11.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
12. 12.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
13. 13.💡 An LED is joined to a 9 V battery through a 470 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) may burn out (b) does not light (c) lights up
14. 14.🔺 A current of 3 A flows when 45 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.True or false: to switch off empty rooms wastes electricity. (a) False (b) True
16. 16.🧮 Resistors of 150 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
17. 17.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
18. 18.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a diode (c) a capacitor (d) a buzzer
19. 19.Which of these wastes electricity? (a) leave the TV on standby (b) close the fridge quickly (c) set the AC to 24 °C (d) use daylight to read
20. 20.🌈 A resistor has the colour bands green, grey, red. What is its value in kilo-ohms (kΩ)? =
21. 21.What does a diode do? (a) lets current go one way (b) makes things spin (c) smooths a wobbly supply (d) stores a little charge
22. 22.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
23. 23.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
24. 24.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
25. 25.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
26. 26.⚡ An 18 W device works on 9 V. What current does it take (in amperes)? =
27. 27.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
28. 28.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = R ÷ V (d) I = V ÷ R
29. 29.📏 Which unit measures the push of a cell? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
30. 30.🔺 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
31. 31.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) more than either one (c) their sum (d) always zero
32. 32.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
33. 33.Which of these saves electricity? (a) leave the TV on standby (b) iron one shirt at a time (c) close the fridge quickly (d) leave fridge door open
34. 34.Which of these is measured in volts (V)? (a) resistance (b) energy used each second (c) power (d) voltage
35. 35.🌈 In the resistor colour code, which number does grey stand for?
36. 36.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
38. 38.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
39. 39.True or false: a diode lets current go one way. (a) False (b) True
40. 40.🧮 A 20 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?

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