Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 854 · 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.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 watt
2. 2.🔺 A 15 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
3. 3.🌈 A resistor has the colour bands violet, blue, brown. What is its value (in ohms)?
4. 4.⚡ A 1.5 W device works on 6 V. What current does it take (in amperes)? =
5. 5.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
6. 6.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.⚡ A device works on 5 V and takes 1 A. What is its power (in watts)? =
8. 8.📏 How many kilo-ohms (kΩ) is 5800 Ω? =
9. 9.🔺 A current of 2.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
10. 10.🧮 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
11. 11.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
12. 12.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
13. 13.⚡ A device works on 12 V and takes 0.5 A. What is its power (in watts)? =
14. 14.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
15. 15.⚡ A device works on 5 V and takes 0.1 A. What is its power (in watts)? =
16. 16.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) zero (d) bigger
17. 17.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
18. 18.True or false: voltage is measured in amperes (A). (a) False (b) True
19. 19.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V ÷ R (c) I = V + R (d) I = R ÷ V
21. 21.🧮 Resistors of 33 Ω, 330 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
22. 22.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
23. 23.💡 An LED is joined to a 6 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) may burn out (c) lights up
24. 24.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
25. 25.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) a filament bulb (d) an oil lamp
26. 26.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
27. 27.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
28. 28.🔺 A 4 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
29. 29.True or false: the voltmeter measures current. (a) False (b) True
30. 30.⚡ A 9 W device works on 6 V. What current does it take (in amperes)? =
31. 31.🔺 A current of 1.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
32. 32.💡 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) does not light (b) may burn out (c) lights up
33. 33.Which of these is measured in volts (V)? (a) voltage (b) resistance (c) power (d) how much a part resists
34. 34.Which of these is measured in watts (W)? (a) power (b) current (c) the push of a cell (d) the flow of charge
35. 35.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
36. 36.⚡ A 1.2 W device works on 12 V. What current does it take (in amperes)? =
37. 37.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V ÷ I (c) R = I ÷ V (d) R = V × I
38. 38.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🧩 Which component blows if current is high? (a) motor (b) resistor (c) LED (d) fuse
40. 40.True or false: an LED has coloured bands. (a) False (b) True

Free electronics lessons, practice and worksheets at talentjr.in/electronics-for-kids