Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 290 · 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.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
2. 2.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
3. 3.📏 How many milliamperes (mA) is 0.04 A?
4. 4.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = R ÷ V (d) I = V ÷ R
5. 5.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a fuse (c) an LED (d) a motor
6. 6.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to make it brighter (d) to store charge
7. 7.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
8. 8.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.🧾 A 50 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
10. 10.What does a thermistor do? (a) lets current go one way (b) smooths a wobbly supply (c) senses how hot it is (d) senses how bright it is
11. 11.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
12. 12.🌈 A resistor has the colour bands green, blue, red. What is its value (in ohms)?
13. 13.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
14. 14.🌈 A resistor has the colour bands white, red, red. What is its value in kilo-ohms (kΩ)? =
15. 15.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
16. 16.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
17. 17.True or false: power is measured in watts (W). (a) False (b) True
18. 18.📏 How many ohms (Ω) is 2.1 kΩ?
19. 19.🔺 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
20. 20.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) more than either one (d) less than either one
21. 21.🧩 Which component is a resistance knob? (a) potentiometer (b) resistor (c) diode (d) fuse
22. 22.Which of these is measured in amperes (A)? (a) the push of a cell (b) resistance (c) voltage (d) the flow of charge
23. 23.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
24. 24.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
25. 25.True or false: an LDR senses how bright it is. (a) False (b) True
26. 26.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4200 Ω resistor? (a) red-yellow-red (b) yellow-red-red (c) yellow-red-orange (d) yellow-red-brown
27. 27.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 volt
28. 28.True or false: a resistor has coloured bands. (a) True (b) False
29. 29.🧮 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)?
30. 30.🧩 Which component turns a fan or wheels? (a) motor (b) capacitor (c) resistor (d) diode
31. 31.True or false: to use old filament bulbs wastes electricity. (a) True (b) False
32. 32.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the one nearest an end (d) the gold band
33. 33.🔺 A current of 50 mA flows when 11 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.True or false: energy used each second is measured in ohms (Ω). (a) True (b) False
35. 35.🧮 A 47 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
36. 36.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
37. 37.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
38. 38.📏 Which unit measures energy used each second? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
39. 39.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
40. 40.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False

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