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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 879 · 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.⚡ A device works on 9 V and takes 0.2 A. What is its power (in watts)? =
  2. 2.🔺 A 2 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  3. 3.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
  4. 4.🌈 A resistor has the colour bands blue, brown, red. What is its value in kilo-ohms (kΩ)? =
  5. 5.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) use daylight to read (c) close the fridge quickly (d) run fans in empty rooms
  6. 6.🔺 A current of 0.5 A flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it makes a sound (d) it changes colour
  8. 8.🔍 Which is the odd one out? (a) use daylight to read (b) leave the TV on standby (c) use old filament bulbs (d) iron one shirt at a time
  9. 9.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
  10. 10.🧮 Resistors of 10 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
  11. 11.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) less than either one (d) always zero
  12. 12.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  13. 13.What does a potentiometer do? (a) is a resistance knob (b) senses how hot it is (c) senses how bright it is (d) turns a fan or wheels
  14. 14.True or false: a thermistor senses how hot it is. (a) True (b) False
  15. 15.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the water tank lid (c) the tap handle (d) the water pressure
  16. 16.🔺 A current of 2.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  17. 17.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
  18. 18.Which of these is measured in ohms (Ω)? (a) how much a part resists (b) power (c) the flow of charge (d) energy used each second
  19. 19.Which of these is measured in ohms (Ω)? (a) resistance (b) energy used each second (c) the flow of charge (d) current
  20. 20.🧮 A 7 V battery is joined to 3 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  21. 21.🔺 A current of 0.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.🧾 A 500 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
  23. 23.What does a resistor do? (a) limits the current (b) smooths a wobbly supply (c) senses how hot it is (d) turns a fan or wheels
  24. 24.💡 An LED is joined to a 6 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) may burn out (c) lights up
  25. 25.🌈 A resistor has the colour bands yellow, brown, red. What is its value (in ohms)?
  26. 26.📏 Which unit measures resistance? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
  27. 27.🔺 A current of 1.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  28. 28.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
  29. 29.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  30. 30.🧾 A 1500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
  31. 31.🧾 A family uses 90 units of electricity in a month and each unit costs ₹8. What is the bill (in ₹)?
  32. 32.True or false: the push of a cell is measured in watts (W). (a) True (b) False
  33. 33.What does a thermistor do? (a) makes things spin (b) smooths a wobbly supply (c) senses how hot it is (d) has coloured bands
  34. 34.🌈 In the resistor colour code, which number does yellow stand for?
  35. 35.⚡ A 4.5 W device works on 1.5 V. What current does it take (in amperes)? =
  36. 36.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
  37. 37.📏 Which unit measures energy used each second? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
  38. 38.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🔺 A current of 50 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. 1.8
  2. 0.2
  3. 25
  4. 6.1
  5. run fans in empty rooms
  6. 5
  7. it does not light
  8. use daylight to read
  9. a motor
  10. 60
  11. less than either one
  12. cathode (−)
  13. is a resistance knob
  14. True
  15. the water pressure
  16. 6
  17. P = V × I
  18. how much a part resists
  19. resistance
  20. 1
  21. 6
  22. 3
  23. limits the current
  24. may burn out
  25. 4100
  26. ohm (Ω)
  27. 15
  28. 595
  29. 230
  30. 6
  31. 720
  32. False
  33. senses how hot it is
  34. 4
  35. 3
  36. energy used each second
  37. watt (W)
  38. 0.75
  39. 4
  40. 12.5

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