Worksheet: Light-emitting Diodes

In this worksheet, we will practice identifying the action of LEDs in circuits

Q1:

The diagram shows a circuit containing several diodes and LEDs. How many of the LEDs in the circuit are lit?

Q2:

The diagram shows 3 LEDs connected in parallel with a cell and a resistor. Which of the LEDs will emit light in this circuit?

  • ALED A
  • BLED B
  • CLED C
  • DLED A and LED C
  • ELED A and LED B

Q3:

The diagram shows a circuit containing several diodes and LEDs. How many of the LEDs in the circuit are lit?

Q4:

The diagram shows a circuit containing a cell, a resistor, and an LED. The LED does not turn on. Which of the following reasons explains why?

  • AAn LED can only be used with alternating current power sources. A cell provides direct current, so the LED will not work.
  • BAn LED is a type of diode. Current only flows in one direction through a diode, and in this circuit, the diode is connected in the wrong direction to allow current through it.
  • CAn LED cannot be placed in series with a resistor.
  • DThe current through the LED is too large. LEDs can only work with small currents.
  • EAn LED can only be used in logic circuits.

Q5:

Which of the following correctly describes an LED?

  • AAn LED is a type of diode that emits light.
  • BAn LED is a type of resistor; the resistance of an LED decreases as the amount of light incident on it increases.
  • CAn LED is a type of resistor; the resistance of an LED decreases as the temperature of the LED increases.
  • DAn LED is a type of diode that only allows current through in one direction when the light incident upon it is greater than a certain amount.
  • EAn LED is a type of diode that emits sound waves at a specific frequency.

Q6:

Which of the following circuit symbols represents an LED?

  • A
  • B
  • C
  • D
  • E

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