Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 229 · 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.📏 How many kilowatts (kW) is 1600 W? =
2. 2.What does a potentiometer do? (a) blows if current is high (b) has coloured bands (c) beeps for an alarm (d) is a resistance knob
3. 3.🌈 In the resistor colour code, which number does black stand for?
4. 4.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 ampere (c) 1 volt (d) 1 watt
5. 5.🔺 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
6. 6.⚡ A device works on 3 V and takes 2 A. What is its power (in watts)? =
7. 7.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the colour of light (d) the length of a wire
8. 8.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
9. 9.📏 Which unit measures energy used each second? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
10. 10.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a buzzer (c) a diode (d) a capacitor
11. 11.🔺 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
12. 12.🌈 A resistor has the colour bands yellow, yellow, orange. What is its value (in ohms)?
13. 13.🔺 A current of 2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
14. 14.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it changes colour (d) it makes a sound
15. 15.🧮 A 100 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)?
16. 16.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to limit the current (d) to make it brighter
17. 17.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
18. 18.🌈 A resistor has the colour bands orange, white, yellow. What is its value in kilo-ohms (kΩ)? =
19. 19.🧩 Which component makes a beeping sound? (a) thermistor (b) buzzer (c) LED (d) resistor
20. 20.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
22. 22.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) bigger (d) smaller
23. 23.🌈 In the resistor colour code, which number does orange stand for?
24. 24.🔺 A current of 20 mA flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
26. 26.💡 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?
27. 27.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
28. 28.🧮 A 100 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
29. 29.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 80000 Ω resistor? (a) grey-black-yellow (b) grey-black-red (c) white-grey-orange (d) grey-black-orange
30. 30.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
31. 31.💡 Does it save or waste electricity to use daylight to read? (a) saves electricity (b) wastes electricity
32. 32.True or false: to unplug idle chargers wastes electricity. (a) False (b) True
33. 33.📏 Which unit measures the flow of charge? (a) watt (W) (b) volt (V) (c) ohm (Ω) (d) ampere (A)
34. 34.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
35. 35.📏 How many kilo-ohms (kΩ) is 9700 Ω? =
36. 36.🌈 In the resistor colour code, which number does yellow stand for?
37. 37.🔺 A current of 40 mA flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.True or false: to switch off empty rooms saves electricity. (a) True (b) False
39. 39.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
40. 40.True or false: the voltmeter is joined across a part. (a) True (b) False

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