Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 791 · 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.What does an LDR do? (a) has coloured bands (b) smooths a wobbly supply (c) blows if current is high (d) senses how bright it is
2. 2.📏 How many amperes (A) is 440 mA? =
3. 3.🔺 A current of 0.2 A flows when 0.6 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.True or false: the ammeter is joined in series. (a) True (b) False
5. 5.🔺 A 5 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
6. 6.🧮 A 3.2 V battery is joined to 10 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
7. 7.⚡ A 36 W device works on 24 V. What current does it take (in amperes)? =
8. 8.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a filament bulb (d) a candle
9. 9.💡 Does it save or waste electricity to unplug idle chargers? (a) wastes electricity (b) saves electricity
10. 10.🧾 A 250 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
11. 11.True or false: a transistor beeps for an alarm. (a) False (b) True
12. 12.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
13. 13.🧮 A 1.5 V battery is joined to 3 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
14. 14.🧮 Resistors of 20 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
15. 15.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to limit the current (d) to make it brighter
16. 16.Which of these is measured in amperes (A)? (a) how much a part resists (b) current (c) the push of a cell (d) voltage
17. 17.🧮 A 1.5 V battery is joined to 5 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
18. 18.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
19. 19.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
20. 20.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
21. 21.💡 A red LED uses 2 V and should get 20 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
22. 22.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
23. 23.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
24. 24.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
25. 25.What does a thermistor do? (a) stores a little charge (b) senses how bright it is (c) blows if current is high (d) senses how hot it is
26. 26.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) switch off empty rooms (c) use daylight to read (d) iron one shirt at a time
27. 27.💡 An LED is joined to a 12 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) lights up (c) may burn out
28. 28.🔺 An 8 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
29. 29.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
30. 30.🔺 A current of 2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
32. 32.🌈 A resistor has the colour bands yellow, green, orange. What is its value in kilo-ohms (kΩ)? =
33. 33.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
34. 34.🧮 Resistors of 10 Ω, 47 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
35. 35.🌈 A resistor has the colour bands yellow, yellow, orange. What is its value in kilo-ohms (kΩ)? =
36. 36.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
37. 37.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.🧩 A capacitor in a circuit can … (a) make light (b) measure heat (c) store charge briefly (d) spin a wheel
39. 39.Which of these is measured in volts (V)? (a) current (b) resistance (c) power (d) voltage
40. 40.⚡ A device works on 3 V and takes 0.1 A. What is its power (in watts)? =

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