Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 437 · 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 3 V and takes 0.1 A. What is its power (in watts)? =
2. 2.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 550 Ω resistor? (a) green-green-red (b) green-blue-brown (c) green-green-black (d) green-green-brown
3. 3.What does a thermistor do? (a) is a resistance knob (b) senses how hot it is (c) limits the current (d) smooths a wobbly supply
4. 4.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
5. 5.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = I ÷ V (d) P = V + I
6. 6.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets smaller (d) gets bigger
7. 7.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
8. 8.⚡ A device works on 1.5 V and takes 1 A. What is its power (in watts)? =
9. 9.🌈 A resistor has the colour bands red, grey, orange. What is its value (in ohms)?
10. 10.⚡ A 1.25 W device works on 5 V. What current does it take (in amperes)? =
11. 11.📏 Which unit measures voltage? (a) watt (W) (b) ampere (A) (c) volt (V) (d) ohm (Ω)
12. 12.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.💡 An LED is joined to a 9 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
14. 14.🧩 Which component has coloured bands? (a) fuse (b) resistor (c) motor (d) potentiometer
15. 15.🧾 A 200 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
16. 16.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a motor (d) a fuse
17. 17.🧮 A 16 V battery is joined to 6 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
18. 18.🔍 Which is the odd one out? (a) use daylight to read (b) iron one shirt at a time (c) use LED lamps (d) close the fridge quickly
19. 19.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
20. 20.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
21. 21.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
22. 22.True or false: a potentiometer is a resistance knob. (a) False (b) True
23. 23.True or false: current is measured in watts (W). (a) True (b) False
24. 24.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2800 Ω resistor? (a) grey-red-red (b) red-grey-brown (c) red-grey-orange (d) red-grey-red
25. 25.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
26. 26.True or false: the ammeter measures voltage. (a) False (b) True
27. 27.What does a diode do? (a) beeps for an alarm (b) lets current go one way (c) makes a beeping sound (d) is a resistance knob
28. 28.🧩 Which component boosts a small signal? (a) motor (b) resistor (c) buzzer (d) transistor
29. 29.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) less than either one (d) always zero
30. 30.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 25 % (c) 50 % (d) 5 %
31. 31.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
32. 32.📏 How many milliamperes (mA) is 3 A?
33. 33.True or false: to run fans in empty rooms saves electricity. (a) False (b) True
34. 34.🔺 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
35. 35.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) smaller (d) zero
36. 36.📏 In the water-pipe picture of a circuit, resistance is like … (a) a bigger tank (b) a narrow pipe (c) the flow of water (d) the water pressure
37. 37.Which of these is measured in volts (V)? (a) energy used each second (b) the push of a cell (c) power (d) resistance
38. 38.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.🌈 A resistor has the colour bands red, violet, orange. What is its value (in ohms)?
40. 40.True or false: to use daylight to read saves electricity. (a) False (b) True

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