Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 11 · 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 home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
2. 2.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
3. 3.💡 An LED is joined to a 3 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) lights up (c) does not light
4. 4.🔺 An 8 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
5. 5.🔺 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
6. 6.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
7. 7.Which of these wastes electricity? (a) close the fridge quickly (b) use old filament bulbs (c) use LED lamps (d) set the AC to 24 °C
8. 8.What does an LED do? (a) has coloured bands (b) limits the current (c) smooths a wobbly supply (d) glows using little power
9. 9.🔺 A current of 40 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
10. 10.🔺 A 2 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
11. 11.🔺 A current of 25 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
12. 12.⚡ 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
13. 13.🔍 Which is the odd one out? (a) iron one shirt at a time (b) leave the TV on standby (c) use old filament bulbs (d) close the fridge quickly
14. 14.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
15. 15.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
16. 16.📏 How many milliamperes (mA) is 0.11 A?
17. 17.True or false: voltage is measured in volts (V). (a) False (b) True
18. 18.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
19. 19.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
20. 20.🔺 A current of 25 mA flows when 5.5 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 1000 (c) 100 (d) 10
22. 22.True or false: voltage is measured in amperes (A). (a) False (b) True
23. 23.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
24. 24.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.📏 How many kilo-ohms (kΩ) is 2600 Ω? =
26. 26.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = R ÷ I (c) V = I × R (d) V = I ÷ R
28. 28.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
29. 29.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
30. 30.Which of these is measured in ohms (Ω)? (a) power (b) the push of a cell (c) how much a part resists (d) energy used each second
31. 31.🧩 Which component makes things spin? (a) LDR (b) potentiometer (c) fuse (d) motor
32. 32.📏 How many watts (W) is 1.4 kW?
33. 33.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the tap handle (c) the pipe colour (d) the water tank lid
34. 34.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) store charge briefly (d) measure heat
35. 35.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
36. 36.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
37. 37.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) less than either one (d) their sum
39. 39.🌈 A resistor has the colour bands yellow, violet, black. What is its value (in ohms)?
40. 40.🔺 A current of 50 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?

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