Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 665 · 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 5 V and takes 3 A. What is its power (in watts)? =
2. 2.🧮 A 22 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
3. 3.🧾 A 250 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
4. 4.📏 How many kilowatts (kW) is 400 W? =
5. 5.🔺 A 16 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
6. 6.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
7. 7.🔺 A current of 0.25 A flows when 0.5 V is joined across a resistor. What is its resistance (in ohms)?
8. 8.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
9. 9.🔺 A current of 0.1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
10. 10.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it does not light (c) it lights brighter (d) it changes colour
11. 11.💡 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)?
12. 12.🧮 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)?
13. 13.🔺 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
14. 14.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
15. 15.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
16. 16.📏 How many watts (W) is 0.9 kW?
17. 17.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
18. 18.🌈 A resistor has the colour bands green, red, orange. What is its value (in ohms)?
19. 19.🌈 A resistor has the colour bands grey, white, brown. What is its value (in ohms)?
20. 20.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
21. 21.🧮 Two equal 220 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
22. 22.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 0 % (d) 50 %
23. 23.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
24. 24.🧮 Resistors of 10 Ω, 47 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
25. 25.🔺 A 36 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
26. 26.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 30 Ω resistor? (a) yellow-orange-black (b) orange-black-black (c) orange-black-brown (d) yellow-black-black
27. 27.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V + I (c) R = V × I (d) R = V ÷ I
28. 28.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to change its colour (d) to limit the current
29. 29.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) becomes zero (c) gets smaller (d) stays the same
31. 31.⚡ A device works on 3 V and takes 0.25 A. What is its power (in watts)? =
32. 32.💡 An LED is joined to a 3 V battery through a 1000 Ω 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
33. 33.🔺 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
34. 34.True or false: the voltmeter measures current. (a) True (b) False
35. 35.🧩 Which component senses how bright it is? (a) resistor (b) capacitor (c) LDR (d) potentiometer
36. 36.🔺 A current of 2.5 A flows when 25 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🌈 A resistor has the colour bands yellow, grey, black. What is its value (in ohms)?
38. 38.📏 Which unit measures how much a part resists? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
39. 39.🔺 A current of 0.25 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.🔺 A 1 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =

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