Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 143 · 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.🌈 In the resistor colour code, which number does red stand for?
2. 2.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
3. 3.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
4. 4.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
5. 5.🔺 A current of 2.5 A flows when 50 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.🌈 A resistor has the colour bands white, grey, orange. What is its value (in ohms)?
7. 7.🔺 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
8. 8.True or false: the ammeter is joined in series. (a) False (b) True
9. 9.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) smaller (d) bigger
10. 10.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
11. 11.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
12. 12.🧾 A 250 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
13. 13.🧩 A capacitor in a circuit can … (a) measure heat (b) store charge briefly (c) make light (d) spin a wheel
14. 14.🔺 A current of 0.25 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.🔺 A 6.25 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.🧩 Which component glows using little power? (a) LDR (b) motor (c) resistor (d) LED
17. 17.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
18. 18.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🧮 Resistors of 20 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
20. 20.📏 Which unit measures how much a part resists? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
21. 21.📏 Which unit measures current? (a) watt (W) (b) ampere (A) (c) ohm (Ω) (d) volt (V)
22. 22.True or false: a motor turns a fan or wheels. (a) False (b) True
23. 23.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a candle (d) a filament bulb
24. 24.🔺 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
25. 25.🌈 A resistor has the colour bands orange, green, red. What is its value in kilo-ohms (kΩ)? =
26. 26.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🧾 A 100 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
28. 28.🔍 Which is the odd one out? (a) iron one shirt at a time (b) use old filament bulbs (c) use LED lamps (d) run fans in empty rooms
29. 29.🔺 A current of 10 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
31. 31.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
32. 32.What does a transistor do? (a) lets current go one way (b) makes a beeping sound (c) boosts a small signal (d) has coloured bands
33. 33.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to store charge (d) to limit the current
34. 34.🧾 A 200 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
35. 35.🔺 A current of 1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
36. 36.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
37. 37.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🌈 In the resistor colour code, which number does black stand for?
39. 39.🌈 A resistor has the colour bands blue, red, red. What is its value (in ohms)?
40. 40.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) always zero (d) less than either one

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