Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 272 · 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 leg by the flat edge is the anode (+). (a) False (b) True
2. 2.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) zero (d) bigger
3. 3.🧮 Resistors of 220 Ω, 68 Ω, 100 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
4. 4.🔺 A current of 0.2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an oil lamp (c) a candle (d) an LED lamp
6. 6.🧮 A 0.4 V battery is joined to 2 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
7. 7.🧩 Which component has coloured bands? (a) diode (b) resistor (c) LDR (d) capacitor
8. 8.🌈 A resistor has the colour bands grey, yellow, orange. What is its value in kilo-ohms (kΩ)? =
9. 9.🌈 A resistor has the colour bands grey, violet, brown. What is its value (in ohms)?
10. 10.What does a thermistor do? (a) glows using little power (b) limits the current (c) senses how hot it is (d) smooths a wobbly supply
11. 11.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it lights brighter (c) it does not light (d) it makes a sound
12. 12.🔺 A 5 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
13. 13.🧮 A 5 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
14. 14.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
15. 15.Which of these saves electricity? (a) run fans in empty rooms (b) leave the TV on standby (c) use daylight to read (d) iron one shirt at a time
16. 16.True or false: a potentiometer is a resistance knob. (a) False (b) True
17. 17.True or false: the ammeter measures current. (a) True (b) False
18. 18.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 0 % (c) 5 % (d) 50 %
19. 19.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
20. 20.🔺 A current of 3 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) gets bigger (d) stays the same
22. 22.🔺 A 1.2 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
23. 23.🔺 A 1 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
24. 24.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
25. 25.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
26. 26.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
27. 27.🧩 Which component turns a fan or wheels? (a) motor (b) transistor (c) LDR (d) diode
28. 28.🔺 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
29. 29.⚡ A device works on 5 V and takes 3 A. What is its power (in watts)? =
30. 30.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
31. 31.🧮 A 1 V battery is joined to 4 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
32. 32.True or false: to leave the TV on standby saves electricity. (a) False (b) True
33. 33.Which of these is measured in ohms (Ω)? (a) voltage (b) how much a part resists (c) power (d) the push of a cell
34. 34.🔺 A 4.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
35. 35.What does a buzzer do? (a) boosts a small signal (b) glows using little power (c) makes a beeping sound (d) lets current go one way
36. 36.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 3 V supply. What current flows (in mA)?
37. 37.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
38. 38.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
39. 39.What does a diode do? (a) lets current go one way (b) beeps for an alarm (c) glows using little power (d) blows if current is high
40. 40.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?

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