Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 860 · 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 40 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🧮 Resistors of 150 Ω, 220 Ω, 47 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
3. 3.💡 An LED is joined to a 6 V battery with no 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
4. 4.Which of these saves electricity? (a) leave the TV on standby (b) use old filament bulbs (c) leave fridge door open (d) use daylight to read
5. 5.🔺 A current of 25 mA flows when 8.25 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
7. 7.⚡ A device works on 9 V and takes 0.2 A. What is its power (in watts)? =
8. 8.🌈 A resistor has the colour bands green, black, black. What is its value (in ohms)?
9. 9.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
10. 10.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
11. 11.What does a potentiometer do? (a) smooths a wobbly supply (b) is a resistance knob (c) senses how hot it is (d) stores a little charge
12. 12.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = V + I (d) P = I ÷ V
13. 13.Which of these saves electricity? (a) leave fridge door open (b) unplug idle chargers (c) leave the TV on standby (d) use old filament bulbs
14. 14.🧮 A 20 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
15. 15.True or false: a diode lets current go one way. (a) True (b) False
16. 16.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
17. 17.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
18. 18.🌈 A resistor has the colour bands red, blue, black. What is its value (in ohms)?
19. 19.True or false: to switch off empty rooms saves electricity. (a) False (b) True
20. 20.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.🧾 A 250 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
22. 22.🔺 A current of 2.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
23. 23.📏 How many ohms (Ω) is 1.3 kΩ?
24. 24.🔺 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
25. 25.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
26. 26.🔺 A current of 10 mA flows when 2.2 V is joined across a resistor. What is its resistance (in ohms)?
27. 27.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) ampere (A) (c) watt (W) (d) volt (V)
28. 28.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
29. 29.True or false: a thermistor limits the current. (a) True (b) False
30. 30.💡 An LED is joined to a 5 V battery through a 220 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) does not light (c) lights up
31. 31.True or false: energy used each second is measured in volts (V). (a) False (b) True
32. 32.🧾 A 500 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
33. 33.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the one nearest an end (d) the gold band
34. 34.🧩 Which component smooths a wobbly supply? (a) LED (b) capacitor (c) motor (d) buzzer
35. 35.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
36. 36.🌈 In the resistor colour code, which number does red stand for?
37. 37.What does a buzzer do? (a) stores a little charge (b) smooths a wobbly supply (c) makes a beeping sound (d) makes things spin
38. 38.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
39. 39.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
40. 40.🔺 A 6 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =

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