Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 495 · 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.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
2. 2.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 420 Ω resistor? (a) red-yellow-brown (b) yellow-red-brown (c) yellow-red-red (d) yellow-red-black
3. 3.🔺 A current of 20 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the gold band (d) the one nearest an end
5. 5.🧮 Resistors of 220 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2600 Ω resistor? (a) red-blue-brown (b) blue-red-red (c) red-blue-orange (d) red-blue-red
8. 8.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
9. 9.What does an LED do? (a) senses how hot it is (b) blows if current is high (c) glows using little power (d) lets current go one way
10. 10.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
11. 11.🔺 A 0.8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
12. 12.Which of these is measured in ohms (Ω)? (a) the push of a cell (b) power (c) energy used each second (d) how much a part resists
13. 13.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) stay the same (d) bigger
14. 14.🔍 Which is the odd one out? (a) iron one shirt at a time (b) use old filament bulbs (c) run fans in empty rooms (d) use LED lamps
15. 15.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it changes colour (d) it makes a sound
16. 16.True or false: voltage is measured in watts (W). (a) False (b) True
17. 17.True or false: the voltmeter measures current. (a) False (b) True
18. 18.🌈 In the resistor colour code, which number does red stand for?
19. 19.🧾 A 200 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
20. 20.🔺 A current of 2 A flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🧾 A 2000 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
22. 22.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
23. 23.🔺 A 3 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
24. 24.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
25. 25.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
26. 26.🌈 A resistor has the colour bands brown, orange, brown. What is its value (in ohms)?
27. 27.📏 How many amperes (A) is 1830 mA? =
28. 28.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
29. 29.🔺 A current of 0.2 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.🧮 An 18 V battery is joined to 6 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
31. 31.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
32. 32.🔺 A current of 2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a resistor (c) a motor (d) an LED
34. 34.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
35. 35.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
36. 36.📏 How many kilowatts (kW) is 3700 W? =
37. 37.🔺 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
38. 38.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🧮 A 2.5 V battery is joined to 4 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
40. 40.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 50 % (d) 25 %

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