Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 819 · 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 0.6 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
2. 2.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
3. 3.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
4. 4.🔺 A 24 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
5. 5.📏 How many ohms (Ω) is 6.6 kΩ?
6. 6.🔺 A 23.5 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
7. 7.🌈 A resistor has the colour bands brown, yellow, orange. What is its value (in ohms)?
8. 8.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the tap handle (c) the water tank lid (d) the pipe colour
9. 9.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the flow of water (c) the water pressure (d) a narrow pipe
10. 10.🌈 In the resistor colour code, which number does violet stand for?
11. 11.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
12. 12.🔺 A current of 50 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
13. 13.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) an oil lamp (d) a filament bulb
14. 14.Which of these wastes electricity? (a) unplug idle chargers (b) close the fridge quickly (c) use daylight to read (d) leave the TV on standby
15. 15.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
16. 16.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
17. 17.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
18. 18.⚡ 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
19. 19.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
20. 20.🔺 A current of 1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
21. 21.💡 A red LED uses 2 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
22. 22.🔍 Which is the odd one out? (a) leave the TV on standby (b) set the AC to 24 °C (c) iron one shirt at a time (d) leave fridge door open
23. 23.🧮 A 33 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
24. 24.📏 How many milliamperes (mA) is 1.42 A?
25. 25.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) less than either one (d) more than either one
26. 26.Which of these is measured in ohms (Ω)? (a) resistance (b) energy used each second (c) the push of a cell (d) the flow of charge
27. 27.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) zero (d) smaller
28. 28.💡 A red LED uses 2 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
29. 29.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 5000 Ω resistor? (a) green-black-brown (b) green-black-red (c) green-black-orange (d) blue-green-red
30. 30.🔺 A current of 40 mA flows when 8.8 V is joined across a resistor. What is its resistance (in ohms)?
31. 31.📏 How many milliamperes (mA) is 2.9 A?
32. 32.⚡ A device works on 9 V and takes 3 A. What is its power (in watts)? =
33. 33.Which of these is measured in watts (W)? (a) how much a part resists (b) current (c) voltage (d) power
34. 34.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) measure heat (d) spin a wheel
35. 35.🔺 A current of 0.1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
36. 36.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
37. 37.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
38. 38.💡 An LED is joined to a 6 V battery through a 470 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) may burn out (c) lights up
39. 39.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = R ÷ I (c) V = I + R (d) V = I × R
40. 40.🧩 Which component beeps for an alarm? (a) buzzer (b) diode (c) thermistor (d) fuse

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