Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 173 · 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.🔺 A current of 1.5 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
2. 2.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water tank lid (b) the tap handle (c) the water pressure (d) the pipe colour
3. 3.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
4. 4.Which of these wastes electricity? (a) use daylight to read (b) iron one shirt at a time (c) close the fridge quickly (d) set the AC to 24 °C
5. 5.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 54000 Ω resistor? (a) yellow-green-orange (b) green-yellow-yellow (c) green-yellow-red (d) green-yellow-orange
6. 6.🌈 In the resistor colour code, which number does violet stand for?
7. 7.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
8. 8.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to limit the current (d) to make it brighter
9. 9.🔺 A current of 25 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
10. 10.🔺 A current of 25 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
11. 11.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
12. 12.What does an LED do? (a) limits the current (b) smooths a wobbly supply (c) stores a little charge (d) glows using little power
13. 13.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I + R (c) V = I × R (d) V = I ÷ R
14. 14.🔺 A current of 1.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.🌈 A resistor has the colour bands yellow, black, yellow. What is its value in kilo-ohms (kΩ)? =
16. 16.🔺 A current of 0.2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) any band (d) the gold band
18. 18.🌈 A resistor has the colour bands white, red, orange. What is its value in kilo-ohms (kΩ)? =
19. 19.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
20. 20.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.🧩 Which component limits the current? (a) resistor (b) fuse (c) LED (d) motor
22. 22.🔺 A current of 50 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.True or false: the voltmeter is joined in series. (a) True (b) False
24. 24.📏 How many kilo-ohms (kΩ) is 6400 Ω? =
25. 25.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) their sum (d) less than either one
27. 27.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
28. 28.True or false: an LDR has coloured bands. (a) False (b) True
29. 29.🧮 A 330 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
30. 30.Which of these saves electricity? (a) use LED lamps (b) leave the TV on standby (c) leave fridge door open (d) iron one shirt at a time
31. 31.🧮 Resistors of 68 Ω, 20 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
32. 32.Which of these saves electricity? (a) close the fridge quickly (b) leave the TV on standby (c) run fans in empty rooms (d) leave fridge door open
33. 33.🔺 An 8 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
34. 34.🔺 A current of 1.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
35. 35.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
36. 36.💡 Does it save or waste electricity to unplug idle chargers? (a) wastes electricity (b) saves electricity
37. 37.Which of these is measured in watts (W)? (a) the push of a cell (b) the flow of charge (c) power (d) voltage
38. 38.🔺 A current of 0.2 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
40. 40.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 260 Ω resistor? (a) blue-red-brown (b) red-blue-black (c) red-blue-red (d) red-blue-brown

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