Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 45 · 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 unit measures power? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
2. 2.🧮 A 20 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
3. 3.🔺 A 4 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
4. 4.True or false: resistance is measured in watts (W). (a) True (b) False
5. 5.🔺 A current of 2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
6. 6.📏 Which unit measures the flow of charge? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
7. 7.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) any band (d) the one nearest an end
8. 8.🔺 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
9. 9.💡 An LED is joined to a 3 V battery through a 470 Ω 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
10. 10.📏 How many amperes (A) is 2750 mA? =
11. 11.Which of these is measured in volts (V)? (a) voltage (b) current (c) how much a part resists (d) resistance
12. 12.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets bigger (c) stays the same (d) gets smaller
14. 14.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
15. 15.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
16. 16.💡 An LED is joined to a 9 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) lights up (c) does not light
17. 17.📏 How many amperes (A) is 1160 mA? =
18. 18.True or false: a diode beeps for an alarm. (a) False (b) True
19. 19.📏 How many amperes (A) is 990 mA? =
20. 20.🔺 A current of 2.5 A flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.📏 In the water-pipe picture of a circuit, resistance is like … (a) a bigger tank (b) the flow of water (c) a narrow pipe (d) the water pressure
22. 22.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
23. 23.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🌈 A resistor has the colour bands white, green, red. What is its value in kilo-ohms (kΩ)? =
25. 25.💡 An LED is joined to a 9 V battery through a 330 Ω 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
26. 26.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V + I (c) R = V ÷ I (d) R = V × I
27. 27.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to store charge (d) to limit the current
28. 28.True or false: a capacitor turns a fan or wheels. (a) True (b) False
29. 29.What does a resistor do? (a) has coloured bands (b) stores a little charge (c) boosts a small signal (d) beeps for an alarm
30. 30.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
31. 31.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🔺 A 6 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
33. 33.What does a diode do? (a) makes things spin (b) smooths a wobbly supply (c) lets current go one way (d) stores a little charge
34. 34.True or false: an LED turns a fan or wheels. (a) True (b) False
35. 35.True or false: a thermistor smooths a wobbly supply. (a) False (b) True
36. 36.🧮 Resistors of 50 Ω, 150 Ω, 10 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
37. 37.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
38. 38.🧩 Which component limits the current? (a) transistor (b) motor (c) capacitor (d) resistor
39. 39.🔺 A current of 50 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 29 Ω resistor? (a) white-red-black (b) red-white-brown (c) red-white-black (d) orange-white-black

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