Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 907 · 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 red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
2. 2.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 55 Ω resistor? (a) blue-green-black (b) green-blue-black (c) green-green-black (d) green-green-brown
3. 3.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
4. 4.🧮 A 3.25 V battery is joined to 3 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
5. 5.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
6. 6.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
7. 7.True or false: the flow of charge is measured in amperes (A). (a) False (b) True
8. 8.💡 What does LED stand for? (a) light-emitting diode (b) low energy device (c) light energy dial (d) large electric dial
9. 9.🔺 A current of 1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
10. 10.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
11. 11.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it makes a sound (d) it changes colour
12. 12.🌈 A resistor has the colour bands grey, grey, yellow. What is its value in kilo-ohms (kΩ)? =
13. 13.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) energy used each second (d) the colour of light
14. 14.🌈 A resistor has the colour bands orange, orange, brown. What is its value (in ohms)?
15. 15.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = R ÷ I (c) V = I × R (d) V = I + R
16. 16.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🌈 A resistor has the colour bands brown, red, red. What is its value in kilo-ohms (kΩ)? =
18. 18.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
19. 19.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 60 (d) 1000
20. 20.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = R ÷ V (c) I = V × R (d) I = V ÷ R
21. 21.What does an LED do? (a) senses how bright it is (b) glows using little power (c) turns a fan or wheels (d) makes a beeping sound
22. 22.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 0 % (d) 5 %
23. 23.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V + I (d) P = V × I
24. 24.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
25. 25.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🧮 Three equal 75 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
28. 28.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
29. 29.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
30. 30.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
31. 31.Which of these is measured in volts (V)? (a) current (b) power (c) the push of a cell (d) energy used each second
32. 32.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
33. 33.🧩 Which component turns a fan or wheels? (a) motor (b) transistor (c) resistor (d) potentiometer
34. 34.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) stays the same (c) becomes zero (d) gets bigger
35. 35.🔺 A current of 1.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2500 Ω resistor? (a) red-green-brown (b) red-green-orange (c) green-red-red (d) red-green-red
37. 37.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
38. 38.Which of these is measured in ohms (Ω)? (a) the push of a cell (b) power (c) resistance (d) current
39. 39.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
40. 40.🧮 A 1.1 V battery is joined to 5 Ω and 6 Ω resistors in series. What current flows (in amperes)? =

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