Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 772 · 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.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
2. 2.True or false: the push of a cell is measured in volts (V). (a) True (b) False
3. 3.🌈 A resistor has the colour bands white, blue, red. What is its value in kilo-ohms (kΩ)? =
4. 4.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
5. 5.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
6. 6.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
7. 7.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
8. 8.True or false: energy used each second is measured in amperes (A). (a) False (b) True
9. 9.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
10. 10.🌈 In the resistor colour code, which number does green stand for?
11. 11.🔺 A current of 25 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.⚡ A device works on 1.5 V and takes 1 A. What is its power (in watts)? =
13. 13.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
14. 14.True or false: to leave the TV on standby wastes electricity. (a) False (b) True
15. 15.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V × I (c) R = V + I (d) R = I ÷ V
16. 16.🔺 A current of 0.5 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.⚡ A 2.5 W device works on 5 V. What current does it take (in amperes)? =
18. 18.🧮 Resistors of 68 Ω, 33 Ω, 22 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
19. 19.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) lights up (c) does not light
20. 20.📏 Which unit measures power? (a) ohm (Ω) (b) ampere (A) (c) watt (W) (d) volt (V)
21. 21.True or false: the ammeter is joined across a part. (a) True (b) False
22. 22.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
23. 23.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
24. 24.🧮 Resistors of 47 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
25. 25.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
26. 26.🔺 A 4 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
27. 27.🧩 Which component makes a beeping sound? (a) capacitor (b) fuse (c) thermistor (d) buzzer
28. 28.Which of these is measured in ohms (Ω)? (a) the flow of charge (b) power (c) how much a part resists (d) the push of a cell
29. 29.🧩 Which component stores a little charge? (a) thermistor (b) resistor (c) fuse (d) capacitor
30. 30.🧩 Which component has coloured bands? (a) LDR (b) thermistor (c) resistor (d) motor
31. 31.💡 Why does an LED need a resistor in series? (a) to store charge (b) to limit the current (c) to change its colour (d) to make it brighter
32. 32.🔺 An 8.25 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
33. 33.What does a potentiometer do? (a) has coloured bands (b) beeps for an alarm (c) makes things spin (d) is a resistance knob
34. 34.🔺 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
35. 35.What does an LDR do? (a) blows if current is high (b) makes a beeping sound (c) glows using little power (d) senses how bright it is
36. 36.🌈 A resistor has the colour bands yellow, violet, brown. What is its value (in ohms)?
37. 37.🔺 A 16 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
38. 38.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 25 % (d) 0 %
39. 39.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
40. 40.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) any band (c) the gold band (d) the widest gap

Free electronics lessons, practice and worksheets at talentjr.in/electronics-for-kids