Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 162 · 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.What does an LDR do? (a) limits the current (b) is a resistance knob (c) senses how bright it is (d) blows if current is high
2. 2.💡 An LED is joined to a 5 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) may burn out (c) lights up
3. 3.What does a buzzer do? (a) beeps for an alarm (b) smooths a wobbly supply (c) limits the current (d) lets current go one way
4. 4.🔺 A current of 1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
6. 6.🔺 A current of 0.1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
7. 7.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
8. 8.True or false: a thermistor beeps for an alarm. (a) False (b) True
9. 9.🔺 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
10. 10.⚡ A 24 W device works on 12 V. What current does it take (in amperes)? =
11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 12 Ω resistor? (a) brown-red-black (b) brown-red-brown (c) red-brown-black (d) red-red-black
12. 12.🔺 A current of 20 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.Which of these is measured in watts (W)? (a) voltage (b) energy used each second (c) current (d) resistance
15. 15.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
16. 16.True or false: the voltmeter is joined in series. (a) False (b) True
17. 17.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
18. 18.🧮 A 3.25 V battery is joined to 3 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
19. 19.💡 What does LED stand for? (a) low energy device (b) light-emitting diode (c) light energy dial (d) large electric dial
20. 20.What does a capacitor do? (a) stores a little charge (b) glows using little power (c) is a resistance knob (d) senses how bright it is
21. 21.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) watt (W) (c) volt (V) (d) ampere (A)
22. 22.🌈 A resistor has the colour bands grey, blue, yellow. What is its value in kilo-ohms (kΩ)? =
23. 23.🧩 Which component blows if current is high? (a) LED (b) fuse (c) potentiometer (d) motor
24. 24.⚡ A 72 W device works on 24 V. What current does it take (in amperes)? =
25. 25.🔺 A 12 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
26. 26.📏 Which unit measures voltage? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
27. 27.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 1000 (c) 10 (d) 100
28. 28.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
29. 29.True or false: to use daylight to read saves electricity. (a) False (b) True
30. 30.🧩 Which component beeps for an alarm? (a) diode (b) LED (c) buzzer (d) thermistor
31. 31.What does a thermistor do? (a) lets current go one way (b) turns a fan or wheels (c) senses how bright it is (d) senses how hot it is
32. 32.🔺 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
33. 33.True or false: to leave fridge door open saves electricity. (a) True (b) False
34. 34.🌈 A resistor has the colour bands grey, black, yellow. What is its value in kilo-ohms (kΩ)? =
35. 35.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a resistor (d) a motor
36. 36.True or false: energy used each second is measured in watts (W). (a) False (b) True
37. 37.Which of these is measured in volts (V)? (a) how much a part resists (b) current (c) voltage (d) power
38. 38.⚡ A device works on 12 V and takes 0.1 A. What is its power (in watts)? =
39. 39.🔺 A 12.5 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
40. 40.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a diode (d) a resistor

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