Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 999 · 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 current of 25 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 volt (c) 1 ampere (d) 1 watt
3. 3.🧩 Which component beeps for an alarm? (a) transistor (b) buzzer (c) LDR (d) diode
4. 4.⚡ A device works on 3 V and takes 1.5 A. What is its power (in watts)? =
5. 5.🧩 Which component limits the current? (a) capacitor (b) resistor (c) LED (d) transistor
6. 6.⚡ A device works on 9 V and takes 2 A. What is its power (in watts)? =
7. 7.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a resistor (c) an LED (d) a motor
8. 8.What does a buzzer do? (a) smooths a wobbly supply (b) makes a beeping sound (c) makes things spin (d) senses how bright it is
9. 9.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
10. 10.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
11. 11.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 50 % (d) 25 %
12. 12.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the size of a cell (d) the colour of light
13. 13.True or false: voltage is measured in volts (V). (a) True (b) False
14. 14.💡 An LED is joined to a 3 V battery through a 470 Ω 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
15. 15.🌈 A resistor has the colour bands orange, grey, red. What is its value in kilo-ohms (kΩ)? =
16. 16.💡 Does it save or waste electricity to use daylight to read? (a) saves electricity (b) wastes electricity
17. 17.💡 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?
18. 18.⚡ A 10 W device works on 5 V. What current does it take (in amperes)? =
19. 19.🧩 Which component lets current go one way? (a) LED (b) capacitor (c) potentiometer (d) diode
20. 20.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
21. 21.🔺 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
22. 22.True or false: a motor turns a fan or wheels. (a) True (b) False
23. 23.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) gets smaller (c) becomes zero (d) stays the same
24. 24.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = V × I (d) P = I ÷ V
25. 25.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
26. 26.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
27. 27.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
28. 28.🔺 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
29. 29.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
30. 30.⚡ A device works on 6 V and takes 0.5 A. What is its power (in watts)? =
31. 31.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🔺 A current of 1 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
34. 34.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) a narrow pipe (c) the pipe colour (d) the flow of water
35. 35.💡 A red LED uses 2 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
36. 36.🧩 Which component senses how bright it is? (a) LED (b) LDR (c) thermistor (d) capacitor
37. 37.🔺 A 2.5 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
38. 38.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
39. 39.🔺 A current of 20 mA flows when 4.4 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.True or false: the ammeter is joined in series. (a) False (b) True

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