Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 399 · 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.📏 Which unit measures energy used each second? (a) ampere (A) (b) watt (W) (c) ohm (Ω) (d) volt (V)
2. 2.Which of these is measured in volts (V)? (a) how much a part resists (b) current (c) the flow of charge (d) voltage
3. 3.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
4. 4.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = I ÷ V (d) R = V + I
5. 5.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets smaller (d) gets bigger
6. 6.Which of these wastes electricity? (a) use daylight to read (b) unplug idle chargers (c) close the fridge quickly (d) iron one shirt at a time
7. 7.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = I ÷ V (d) P = V + I
8. 8.🧾 A 2000 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
9. 9.🌈 In the resistor colour code, which number does violet stand for?
10. 10.🔺 A current of 20 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
11. 11.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
12. 12.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🧮 A 7 V battery is joined to 3 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
14. 14.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) the one nearest an end (d) any band
15. 15.🧩 A capacitor in a circuit can … (a) measure heat (b) store charge briefly (c) spin a wheel (d) make light
16. 16.🧩 Which component limits the current? (a) fuse (b) resistor (c) LDR (d) LED
17. 17.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
18. 18.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
19. 19.🧮 A 100 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 310 Ω resistor? (a) orange-brown-brown (b) brown-orange-brown (c) orange-brown-red (d) orange-brown-black
21. 21.🔺 A current of 0.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🧮 A 4.5 V battery is joined to 5 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
23. 23.What does an LED do? (a) is a resistance knob (b) lets current go one way (c) glows using little power (d) boosts a small signal
24. 24.📏 Which unit measures how much a part resists? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
25. 25.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 740 Ω resistor? (a) violet-yellow-brown (b) violet-yellow-black (c) yellow-violet-brown (d) violet-yellow-red
26. 26.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🔺 A current of 20 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.🌈 A resistor has the colour bands green, orange, orange. What is its value in kilo-ohms (kΩ)? =
29. 29.True or false: to use daylight to read saves electricity. (a) True (b) False
30. 30.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
31. 31.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
32. 32.🧮 Resistors of 33 Ω, 68 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
33. 33.📏 How many kilo-ohms (kΩ) is 2500 Ω? =
34. 34.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) less than either one (d) more than either one
35. 35.📏 Which unit measures the push of a cell? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
36. 36.📏 Which unit measures current? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
37. 37.💡 Does it save or waste electricity to unplug idle chargers? (a) wastes electricity (b) saves electricity
38. 38.🧩 Which component senses how bright it is? (a) motor (b) thermistor (c) resistor (d) LDR
39. 39.What does a buzzer do? (a) turns a fan or wheels (b) boosts a small signal (c) lets current go one way (d) beeps for an alarm
40. 40.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?

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