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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 498 · 40 questions
TalentJR

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.

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  1. 1.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V × I (d) P = V ÷ I
  2. 2.🔺 A current of 0.1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  3. 3.🔺 A current of 10 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 100 (b) 1024 (c) 1000 (d) 10
  5. 5.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  6. 6.⚡ A 2.4 W device works on 12 V. What current does it take (in amperes)? =
  7. 7.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  8. 8.🌈 A resistor has the colour bands yellow, black, yellow. What is its value in kilo-ohms (kΩ)? =
  9. 9.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to make it brighter (d) to limit the current
  10. 10.🔺 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
  11. 11.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) a narrow pipe (c) a bigger tank (d) the flow of water
  12. 12.🔍 Which is the odd one out? (a) run fans in empty rooms (b) close the fridge quickly (c) leave the TV on standby (d) iron one shirt at a time
  13. 13.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V ÷ R (c) I = V × R (d) I = V + R
  14. 14.🧮 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
  15. 15.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
  16. 16.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🔺 A current of 3 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  19. 19.True or false: a resistor limits the current. (a) True (b) False
  20. 20.💡 An LED is joined to a 3 V battery through a 330 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
  21. 21.⚡ A device works on 24 V and takes 0.5 A. What is its power (in watts)? =
  22. 22.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 25 % (d) 0 %
  23. 23.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
  24. 24.🔺 A current of 25 mA flows when 3.75 V is joined across a resistor. What is its resistance (in ohms)?
  25. 25.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
  26. 26.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  27. 27.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) lights up (c) may burn out
  28. 28.True or false: a thermistor limits the current. (a) True (b) False
  29. 29.🧮 Resistors of 20 Ω, 10 Ω, 68 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
  30. 30.🧮 A 33 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  31. 31.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.🔺 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
  33. 33.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  34. 34.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.🌈 A resistor has the colour bands red, blue, orange. What is its value in kilo-ohms (kΩ)? =
  36. 36.🧩 Which component has coloured bands? (a) buzzer (b) motor (c) thermistor (d) resistor
  37. 37.🌈 A resistor has the colour bands violet, brown, red. What is its value in kilo-ohms (kΩ)? =
  38. 38.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
  39. 39.📏 How many amperes (A) is 1740 mA? =
  40. 40.🧩 Which component stores a little charge? (a) diode (b) capacitor (c) resistor (d) LDR

Answer key

  1. P = V × I
  2. 0.6
  3. 2.2
  4. 1000
  5. 165
  6. 0.2
  7. 1840
  8. 400
  9. to limit the current
  10. R = V ÷ I
  11. a narrow pipe
  12. close the fridge quickly
  13. I = V ÷ R
  14. less than either one
  15. False
  16. 0.8
  17. 2
  18. 400
  19. True
  20. lights up
  21. 12
  22. 5 %
  23. 0.9
  24. 150
  25. 1150
  26. 500
  27. may burn out
  28. False
  29. 148
  30. 198
  31. 1.2
  32. gets smaller
  33. 5.5
  34. 18
  35. 26
  36. resistor
  37. 7.1
  38. 25
  39. 1.74
  40. capacitor

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