Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 188 · 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 is the odd one out? (a) close the fridge quickly (b) set the AC to 24 °C (c) unplug idle chargers (d) leave the TV on standby
2. 2.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
3. 3.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
4. 4.True or false: the voltmeter measures voltage. (a) False (b) True
5. 5.🔺 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
6. 6.True or false: the push of a cell is measured in ohms (Ω). (a) False (b) True
7. 7.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
8. 8.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.🔺 A current of 2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
10. 10.🔺 A current of 25 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
11. 11.🔍 Which is the odd one out? (a) use old filament bulbs (b) set the AC to 24 °C (c) use daylight to read (d) use LED lamps
12. 12.🧮 A 4.4 V battery is joined to 12 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
13. 13.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
14. 14.📏 How many ohms (Ω) is 3.9 kΩ?
15. 15.💡 An LED is joined to a 9 V battery through a 470 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
16. 16.🌈 In the resistor colour code, which number does orange stand for?
17. 17.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
18. 18.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
19. 19.Which of these is measured in volts (V)? (a) current (b) resistance (c) voltage (d) power
20. 20.🔺 A current of 0.1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) always zero (d) less than either one
22. 22.🔺 A 3 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
23. 23.🔺 A current of 0.1 A flows when 0.2 V is joined across a resistor. What is its resistance (in ohms)?
24. 24.🔺 A 2 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
25. 25.Which of these is measured in volts (V)? (a) resistance (b) energy used each second (c) the push of a cell (d) current
26. 26.Which of these saves electricity? (a) leave the TV on standby (b) switch off empty rooms (c) use old filament bulbs (d) run fans in empty rooms
27. 27.What does an LDR do? (a) blows if current is high (b) senses how bright it is (c) boosts a small signal (d) makes things spin
28. 28.True or false: a potentiometer stores a little charge. (a) True (b) False
29. 29.🔺 A current of 0.25 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
30. 30.💡 An LED is joined to a 6 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) lights up (b) may burn out (c) does not light
31. 31.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 25 % (d) 50 %
32. 32.🔍 Which is the odd one out? (a) leave fridge door open (b) switch off empty rooms (c) leave the TV on standby (d) run fans in empty rooms
33. 33.🌈 In the resistor colour code, which number does grey stand for?
34. 34.💡 An LED is joined to a 9 V battery through a 220 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) may burn out (c) does not light
35. 35.📏 How many kilowatts (kW) is 3400 W? =
36. 36.💡 What does LED stand for? (a) light energy dial (b) light-emitting diode (c) low energy device (d) large electric dial
37. 37.🧾 A 50 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
38. 38.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
39. 39.⚡ A device works on 9 V and takes 0.25 A. What is its power (in watts)? =
40. 40.🧾 A 200 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =

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