Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 542 · 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 2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🔺 A current of 50 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.💡 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?
4. 4.True or false: the ammeter measures voltage. (a) False (b) True
5. 5.🔺 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
6. 6.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets bigger (d) gets smaller
7. 7.💡 Does it save or waste electricity to use old filament bulbs? (a) saves electricity (b) wastes electricity
8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 77 Ω resistor? (a) grey-violet-black (b) violet-violet-black (c) violet-violet-brown (d) violet-grey-black
9. 9.True or false: a thermistor lets current go one way. (a) False (b) True
10. 10.🧾 Which lamp gives the same light for the least power? (a) a candle (b) a filament bulb (c) an LED lamp (d) an oil lamp
11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 64 Ω resistor? (a) blue-yellow-brown (b) violet-yellow-black (c) yellow-blue-black (d) blue-yellow-black
12. 12.True or false: voltage is measured in watts (W). (a) True (b) False
13. 13.🧩 A capacitor in a circuit can … (a) store charge briefly (b) make light (c) spin a wheel (d) measure heat
14. 14.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I × R (c) V = I + R (d) V = R ÷ I
16. 16.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
17. 17.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) stay the same (d) smaller
18. 18.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🔺 A current of 2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
20. 20.🌈 A resistor has the colour bands brown, grey, brown. What is its value (in ohms)?
21. 21.Which of these wastes electricity? (a) leave the TV on standby (b) switch off empty rooms (c) use daylight to read (d) use LED lamps
22. 22.💡 An LED is joined to a 6 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) lights up (c) does not light
23. 23.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
24. 24.🔺 A current of 25 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
25. 25.⚡ A 4.5 W device works on 3 V. What current does it take (in amperes)? =
26. 26.🔺 A current of 1.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
27. 27.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water tank lid (c) the pipe colour (d) the water pressure
28. 28.What does an LDR do? (a) senses how bright it is (b) lets current go one way (c) senses how hot it is (d) smooths a wobbly supply
29. 29.⚡ A 1.2 W device works on 12 V. What current does it take (in amperes)? =
30. 30.Which of these is measured in amperes (A)? (a) voltage (b) the push of a cell (c) the flow of charge (d) how much a part resists
31. 31.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
32. 32.🔺 A current of 25 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
33. 33.📏 Which unit measures how much a part resists? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
34. 34.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 3400 Ω resistor? (a) orange-yellow-orange (b) yellow-orange-red (c) orange-yellow-red (d) orange-yellow-brown
35. 35.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
36. 36.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
37. 37.🌈 A resistor has the colour bands violet, blue, orange. What is its value (in ohms)?
38. 38.📏 How many kilo-ohms (kΩ) is 4100 Ω? =
39. 39.🌈 Which band is read first on a resistor? (a) the gold band (b) the one nearest an end (c) the widest gap (d) any band
40. 40.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?

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