Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 549 · 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.Which of these is measured in watts (W)? (a) current (b) power (c) voltage (d) resistance
2. 2.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 volt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
4. 4.🌈 In the resistor colour code, which number does white stand for?
5. 5.🔺 A current of 0.2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
6. 6.Which of these wastes electricity? (a) switch off empty rooms (b) run fans in empty rooms (c) use daylight to read (d) use LED lamps
7. 7.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
8. 8.🧩 Which component is a resistance knob? (a) buzzer (b) motor (c) LED (d) potentiometer
9. 9.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
10. 10.🔺 A current of 40 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
11. 11.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water tank lid (c) the water pressure (d) the pipe colour
12. 12.📏 How many amperes (A) is 2830 mA? =
13. 13.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
14. 14.🧩 Which component beeps for an alarm? (a) buzzer (b) fuse (c) LDR (d) capacitor
15. 15.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V × R (c) I = V ÷ R (d) I = V + R
16. 16.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the length of a wire (d) the colour of light
17. 17.🔺 A current of 25 mA flows when 6.25 V is joined across a resistor. What is its resistance (in ohms)?
18. 18.⚡ A 0.15 W device works on 1.5 V. What current does it take (in amperes)? =
19. 19.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 100 (c) 10 (d) 1000
21. 21.What does a capacitor do? (a) senses how hot it is (b) is a resistance knob (c) makes things spin (d) stores a little charge
22. 22.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) may burn out (c) does not light
23. 23.💡 What does LED stand for? (a) low energy device (b) large electric dial (c) light energy dial (d) light-emitting diode
24. 24.🔺 A 12.5 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
25. 25.🌈 A resistor has the colour bands red, brown, black. What is its value (in ohms)?
26. 26.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a capacitor (d) a resistor
27. 27.🔺 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
28. 28.🧮 A 4 V battery is joined to 8 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
29. 29.🔺 A 4.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
30. 30.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
31. 31.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to store charge (d) to change its colour
32. 32.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) always zero (d) their sum
33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets bigger (c) gets smaller (d) stays the same
34. 34.🌈 A resistor has the colour bands yellow, black, orange. What is its value (in ohms)?
35. 35.True or false: the voltmeter measures voltage. (a) False (b) True
36. 36.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
37. 37.Which of these saves electricity? (a) run fans in empty rooms (b) use old filament bulbs (c) close the fridge quickly (d) iron one shirt at a time
38. 38.🔺 A current of 20 mA flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
40. 40.True or false: to set the AC to 24 °C wastes electricity. (a) True (b) False

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