Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 830 · 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 home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
2. 2.🔺 A current of 0.2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
3. 3.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
4. 4.🔺 An 11 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
5. 5.Which of these saves electricity? (a) leave fridge door open (b) use daylight to read (c) run fans in empty rooms (d) leave the TV on standby
6. 6.📏 How many milliamperes (mA) is 2.2 A?
7. 7.💡 What does LED stand for? (a) light-emitting diode (b) large electric dial (c) light energy dial (d) low energy device
8. 8.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = I ÷ V (d) P = V + I
9. 9.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
10. 10.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
11. 11.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 50 % (d) 0 %
12. 12.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = V ÷ I (d) R = I ÷ V
13. 13.📏 How many watts (W) is 2.3 kW?
14. 14.🔺 A 7.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
15. 15.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the tap handle (c) the water tank lid (d) the water pressure
16. 16.🌈 A resistor has the colour bands green, blue, red. What is its value (in ohms)?
17. 17.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) always zero (c) more than either one (d) their sum
18. 18.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
19. 19.🔺 A current of 2.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
20. 20.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
21. 21.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the gold band (d) the one nearest an end
22. 22.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
23. 23.📏 In the water-pipe picture of a circuit, resistance is like … (a) a bigger tank (b) the water pressure (c) the flow of water (d) a narrow pipe
24. 24.🧩 Which component senses how hot it is? (a) diode (b) thermistor (c) fuse (d) motor
25. 25.🧮 Resistors of 33 Ω, 10 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
26. 26.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) energy used each second (d) the length of a wire
27. 27.💡 An LED is joined to a 6 V battery through a 220 Ω 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.⚡ A 0.75 W device works on 1.5 V. What current does it take (in amperes)? =
29. 29.🌈 A resistor has the colour bands white, white, red. What is its value (in ohms)?
30. 30.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 ampere (c) 1 volt (d) 1 watt
31. 31.Which of these wastes electricity? (a) iron one shirt at a time (b) use daylight to read (c) use LED lamps (d) unplug idle chargers
32. 32.⚡ A 7.5 W device works on 5 V. What current does it take (in amperes)? =
33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) stays the same (d) gets bigger
34. 34.What does a thermistor do? (a) makes things spin (b) turns a fan or wheels (c) senses how hot it is (d) limits the current
35. 35.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.🔍 Which is the odd one out? (a) use daylight to read (b) iron one shirt at a time (c) run fans in empty rooms (d) leave the TV on standby
38. 38.💡 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) lights up (b) does not light (c) may burn out
39. 39.🔺 A current of 3 A flows when 36 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = I + R (c) V = R ÷ I (d) V = I ÷ R

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