Worksheet: The Power of Electrical Components

In this worksheet, we will practice using the formula E = QV to find the energy dissipated to the environment by the component of an electronic circuit.

Q1:

A 7 Ω resistor and a 5 Ω resistor are connected in series to a cell. The cell provides a current of 4 A through the circuit. How much energy do the resistors transfer to the surrounding environment in 20 seconds?

Q2:

Which of the following is the correct formula for the energy 𝐸 transferred to the environment when an amount of a charge, 𝑄 , is moved across a potential difference, 𝑉 ?

  • A 𝐸 = 𝑉 𝑄
  • B 𝐸 = 𝑄 𝑉
  • C 𝐸 = 1 2 𝑄 𝑉 2
  • D 𝐸 = 𝑄 𝑉
  • E 𝑄 = 𝐸 𝑉

Q3:

An electric motor is connected to a 9 V battery. Over a period of time, the motor converts 450 J of electrical energy into kinetic energy, heat, and sound. How much charge passes through the motor over this period of time?

Q4:

Which of the following is the correct formula for the power supplied to a component of an electrical circuit? 𝑃 is the power supplied to the component, 𝐼 is the current through the component, 𝑉 is the potential difference across the component, and 𝑅 is the resistance of the component.

  • A 𝑃 = 𝑉 𝐼 𝑅
  • B 𝑃 = 𝐼 𝑅
  • C 𝑃 = 𝐼 𝑉
  • D 𝑃 = 𝐼 𝑉
  • E 𝑉 = 𝐼 𝑅

Q5:

The diagram shows a circuit consisting of a light bulb connected to a cell. The potential difference across the bulb is 9 V, and the current through it is 4 A. How much is the power of the light bulb?

Q6:

A 45 mW LED is connected to a 9 V battery and left on for 30 seconds. How much charge passes through the LED over this time?

Q7:

The potential difference across a resistor in a circuit is 10 V. If 150 C of charge passes through the resistor, how much energy is dissipated to the environment by the resistor?

Q8:

A piece of connecting wire in a circuit is 20 cm long. It has a resistance of 0.02 Ω and dissipates energy to its environment as heat at a rate of 2 W. How much is the current passing through the wire?

Q9:

A 4 A current passes through a 10 Ω resistor. How much is the power of the resistor?

Q10:

A bulb is connected to a cell in series. The potential difference across the bulb is 4 V and the current through it is 0.1 A.

How much charge passes through the bulb in 60 seconds?

How much energy does the bulb dissipate as light and heat in 60 seconds?

Q11:

A resistor in a circuit has a potential difference of 12 V across it. It dissipates energy to its environment in the form of heat at a rate of 48 W. How much charge passes through the resistor in 2 minutes?

Q12:

The diagram shows a circuit consisting of three identical resistors connected to a cell. At what rate does one resistor dissipate energy to the surrounding environment?

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