Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 434 · 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) the push of a cell
2. 2.🔺 A 37.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
3. 3.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
4. 4.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
5. 5.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
6. 6.Which of these wastes electricity? (a) leave fridge door open (b) switch off empty rooms (c) use daylight to read (d) close the fridge quickly
7. 7.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 850 Ω resistor? (a) grey-green-brown (b) grey-green-black (c) green-grey-brown (d) grey-green-red
9. 9.🧮 A 12 V battery is joined to 2 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
10. 10.🔺 A 10 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
11. 11.True or false: to use old filament bulbs saves electricity. (a) False (b) True
12. 12.⚡ A device works on 3 V and takes 2 A. What is its power (in watts)? =
13. 13.📏 Which unit measures current? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
14. 14.🌈 In the resistor colour code, which number does grey stand for?
15. 15.🌈 A resistor has the colour bands red, black, black. What is its value (in ohms)?
16. 16.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
17. 17.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to change its colour (d) to limit the current
18. 18.🌈 A resistor has the colour bands grey, violet, yellow. What is its value in kilo-ohms (kΩ)? =
19. 19.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
20. 20.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) stay the same (c) smaller (d) zero
21. 21.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
22. 22.🧮 Two resistors in parallel give a total that is … (a) their sum (b) less than either one (c) always zero (d) more than either one
23. 23.🔺 A current of 40 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
24. 24.True or false: a motor makes things spin. (a) False (b) True
25. 25.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a fuse (c) a motor (d) an LED
26. 26.🔺 A current of 2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🔍 Which is the odd one out? (a) leave fridge door open (b) use daylight to read (c) set the AC to 24 °C (d) switch off empty rooms
28. 28.🔺 A current of 10 mA flows through a 330 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.🔺 A 3 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
31. 31.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
32. 32.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
33. 33.What does a motor do? (a) stores a little charge (b) smooths a wobbly supply (c) makes things spin (d) beeps for an alarm
34. 34.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
35. 35.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
36. 36.🧮 Resistors of 50 Ω, 22 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
37. 37.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
38. 38.🌈 A resistor has the colour bands blue, brown, orange. What is its value (in ohms)?
39. 39.🔺 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
40. 40.🔺 A current of 0.5 A flows when 10 V is joined across a resistor. What is its resistance (in ohms)?

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