Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 780 · 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.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V × I (d) R = V + I
2. 2.🔺 A current of 20 mA flows when 9.4 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.🌈 A resistor has the colour bands violet, brown, red. What is its value in kilo-ohms (kΩ)? =
4. 4.🧮 Resistors of 20 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
5. 5.🧩 Which component glows using little power? (a) motor (b) LED (c) potentiometer (d) resistor
6. 6.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the colour of light (d) the length of a wire
7. 7.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the water pressure (c) the water tank lid (d) the tap handle
8. 8.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.⚡ A 3 W device works on 1.5 V. What current does it take (in amperes)? =
10. 10.💡 An LED is joined to a 12 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) lights up (c) may burn out
11. 11.🧩 Which component lets current go one way? (a) buzzer (b) potentiometer (c) diode (d) fuse
12. 12.💡 An LED is joined to a 6 V battery through a 470 Ω 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
13. 13.Which of these saves electricity? (a) run fans in empty rooms (b) leave fridge door open (c) close the fridge quickly (d) use old filament bulbs
14. 14.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to store charge (c) to make it brighter (d) to change its colour
15. 15.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
16. 16.🧾 A 50 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
17. 17.True or false: current is measured in amperes (A). (a) True (b) False
18. 18.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
19. 19.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
20. 20.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
21. 21.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a resistor (c) a diode (d) a buzzer
22. 22.What does a capacitor do? (a) turns a fan or wheels (b) beeps for an alarm (c) smooths a wobbly supply (d) makes a beeping sound
23. 23.🧮 Resistors of 150 Ω, 10 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
24. 24.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.🧮 Three equal 60 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🔺 A 0.6 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
27. 27.🔺 A current of 0.25 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
28. 28.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
29. 29.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I × R (c) V = I ÷ R (d) V = I + R
30. 30.What does a fuse do? (a) lets current go one way (b) senses how hot it is (c) blows if current is high (d) has coloured bands
31. 31.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🔺 A current of 0.2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🌈 A resistor has the colour bands green, red, yellow. What is its value in kilo-ohms (kΩ)? =
34. 34.📏 How many milliamperes (mA) is 0.68 A?
35. 35.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.Which of these saves electricity? (a) use old filament bulbs (b) iron one shirt at a time (c) use daylight to read (d) leave the TV on standby
37. 37.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.🧩 Which component limits the current? (a) LDR (b) diode (c) resistor (d) motor
39. 39.🧩 Which component boosts a small signal? (a) motor (b) buzzer (c) diode (d) transistor
40. 40.True or false: to set the AC to 24 °C wastes electricity. (a) False (b) True

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