Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 949 · 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.Which of these is measured in amperes (A)? (a) current (b) resistance (c) power (d) energy used each second
2. 2.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I + R (c) V = I ÷ R (d) V = I × R
3. 3.🌈 In the resistor colour code, which number does violet stand for?
4. 4.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
5. 5.What does a capacitor do? (a) turns a fan or wheels (b) makes a beeping sound (c) smooths a wobbly supply (d) boosts a small signal
6. 6.True or false: the ammeter measures voltage. (a) False (b) True
7. 7.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
8. 8.🔺 A current of 25 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
9. 9.True or false: resistance is measured in ohms (Ω). (a) False (b) True
10. 10.🧮 A 4 V battery is joined to 8 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
11. 11.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
12. 12.💡 An LED is joined to a 3 V battery through a 220 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) lights up (c) may burn out
13. 13.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
14. 14.💡 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
15. 15.True or false: the voltmeter measures current. (a) True (b) False
16. 16.💡 What happens if an LED is put in backwards? (a) it does not light (b) it changes colour (c) it lights brighter (d) it makes a sound
17. 17.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
18. 18.💡 What does LED stand for? (a) low energy device (b) large electric dial (c) light energy dial (d) light-emitting diode
19. 19.🔺 A 6 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
20. 20.🔺 A current of 0.1 A flows when 0.6 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🔺 A 3 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
22. 22.🧮 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
23. 23.True or false: a fuse limits the current. (a) True (b) False
24. 24.🔺 A current of 3 A flows when 24 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = R ÷ V (c) I = V + R (d) I = V ÷ R
26. 26.⚡ A device works on 6 V and takes 1 A. What is its power (in watts)? =
27. 27.🔺 A current of 2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
28. 28.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
29. 29.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 50 % (d) 0 %
30. 30.📏 How many kilo-ohms (kΩ) is 9000 Ω? =
31. 31.🌈 A resistor has the colour bands brown, brown, yellow. What is its value in kilo-ohms (kΩ)? =
32. 32.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
33. 33.🧮 Resistors of 68 Ω, 470 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
34. 34.🌈 A resistor has the colour bands blue, red, orange. What is its value (in ohms)?
35. 35.🌈 In the resistor colour code, which number does brown stand for?
36. 36.🔺 A current of 40 mA flows when 8.8 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🔺 A current of 2.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🔺 A current of 3 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
39. 39.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
40. 40.⚡ A device works on 9 V and takes 3 A. What is its power (in watts)? =

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