Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 351 · 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 device works on 12 V and takes 2 A. What is its power (in watts)? =
2. 2.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an oil lamp (d) an LED lamp
3. 3.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 81 Ω resistor? (a) white-brown-black (b) grey-brown-brown (c) grey-brown-black (d) brown-grey-black
4. 4.🌈 A resistor has the colour bands brown, yellow, black. What is its value (in ohms)?
5. 5.🧩 Which component makes things spin? (a) thermistor (b) potentiometer (c) motor (d) buzzer
6. 6.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🔺 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
8. 8.🌈 A resistor has the colour bands blue, white, red. What is its value (in ohms)?
9. 9.True or false: voltage is measured in watts (W). (a) False (b) True
10. 10.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 60 (c) 1000 (d) 100
11. 11.🔺 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
12. 12.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) make light (d) store charge briefly
13. 13.Which of these saves electricity? (a) use old filament bulbs (b) run fans in empty rooms (c) use LED lamps (d) leave fridge door open
14. 14.What does a resistor do? (a) boosts a small signal (b) makes a beeping sound (c) limits the current (d) stores a little charge
15. 15.🧮 Three equal 60 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
16. 16.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = V × I (d) P = I ÷ V
17. 17.📏 How many kilowatts (kW) is 1250 W? =
18. 18.True or false: a capacitor stores a little charge. (a) False (b) True
19. 19.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
20. 20.🔺 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
21. 21.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
22. 22.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
23. 23.📏 How many watts (W) is 4.2 kW?
24. 24.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
25. 25.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
26. 26.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
27. 27.💡 An LED is joined to a 9 V battery through a 1000 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
28. 28.🧩 Which component is a resistance knob? (a) resistor (b) buzzer (c) thermistor (d) potentiometer
29. 29.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) more than either one (d) less than either one
30. 30.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 watt (c) 1 ampere (d) 1 volt
31. 31.⚡ A 2.25 W device works on 1.5 V. What current does it take (in amperes)? =
32. 32.📏 How many watts (W) is 4.4 kW?
33. 33.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = I ÷ V (c) R = V + I (d) R = V ÷ I
34. 34.🧩 Which component glows using little power? (a) fuse (b) LED (c) diode (d) motor
35. 35.What does an LDR do? (a) smooths a wobbly supply (b) blows if current is high (c) glows using little power (d) senses how bright it is
36. 36.Which of these saves electricity? (a) use old filament bulbs (b) run fans in empty rooms (c) switch off empty rooms (d) leave the TV on standby
37. 37.📏 How many kilo-ohms (kΩ) is 9400 Ω? =
38. 38.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it makes a sound (c) it lights brighter (d) it does not light
39. 39.📏 How many watts (W) is 0.7 kW?
40. 40.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =

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