Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 180 · 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 10 W device works on 5 V. What current does it take (in amperes)? =
2. 2.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
3. 3.🌈 A resistor has the colour bands violet, black, red. What is its value in kilo-ohms (kΩ)? =
4. 4.🔺 A current of 2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
5. 5.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
6. 6.🧮 A 150 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)?
7. 7.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the gold band (d) the one nearest an end
8. 8.🔺 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
9. 9.True or false: to leave the TV on standby wastes electricity. (a) True (b) False
10. 10.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) their sum (c) more than either one (d) always zero
11. 11.🔺 A 16.5 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
12. 12.🧩 Which component limits the current? (a) capacitor (b) LED (c) resistor (d) transistor
13. 13.True or false: to leave fridge door open wastes electricity. (a) False (b) True
14. 14.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets smaller (d) gets bigger
16. 16.🔺 A current of 50 mA flows when 16.5 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.🌈 A resistor has the colour bands orange, green, yellow. What is its value in kilo-ohms (kΩ)? =
18. 18.🔺 A 3 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
19. 19.🧩 Which component turns a fan or wheels? (a) LED (b) LDR (c) motor (d) thermistor
20. 20.Which of these is measured in volts (V)? (a) power (b) voltage (c) how much a part resists (d) the flow of charge
21. 21.🔺 A 3 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
22. 22.🔺 A current of 0.25 A flows when 0.75 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🧮 Resistors of 10 Ω, 100 Ω, 150 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
25. 25.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) bigger (d) stay the same
26. 26.⚡ A 6 W device works on 24 V. What current does it take (in amperes)? =
27. 27.🌈 In the resistor colour code, which number does brown stand for?
28. 28.Which of these is measured in amperes (A)? (a) power (b) the flow of charge (c) resistance (d) the push of a cell
29. 29.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
30. 30.💡 An LED is joined to a 5 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) does not light (c) may burn out
31. 31.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
32. 32.🧩 Which component makes things spin? (a) LDR (b) thermistor (c) transistor (d) motor
33. 33.🔺 A current of 20 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🔺 A 10 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
35. 35.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
36. 36.🌈 A resistor has the colour bands yellow, yellow, red. What is its value in kilo-ohms (kΩ)? =
37. 37.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
38. 38.🧾 A 100 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
39. 39.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
40. 40.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =

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