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Electrical Power

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Electrical Power

Electrical power runs the world around us. Thanks to Nikola Tesla's discovery of alternating current (AC) power, homes all around the world receive Electricity. So then what exactly does electrical power have to do with the electricity that powers our appliances? This article will give you a detailed explanation of the definition of power, its equations, and its properties. We will also study the relationship between power, current, voltage, and other quantities. Happy learning!

Electrical power definition

Electric power is defined as the electrical energy transferred in a circuit per unit of time.

The unit of electric power is the Watt () and it is denoted by the symbol. It is often measured in.

The power rating that we see in our home appliances defines how much energy is being transferred from the grid to power the device. A mobile phone charger has a power rating in the range of. This means that the charger drawsorJoules per second from the mains. An electric kettle on the other hand has a power rating of. That isJoules per second which istimes the power consumed by the charger! This makes ittimes more expensive to use than your typical mobile charger. Let us now look at how to calculate the power using the current drawn and the voltage.

Electrical power formula

The electric power transferred to an electrical component in a circuit can be calculated using the electric power formula:

Or in words:

whereis the electrical power,is the potential difference across the component andis the current passing through the component.

The electric power can also be calculated by knowing the current and resistance using the following equation

whereis the resistance of the electrical component.

Therefore,of electric power can be defined as the energy transferred when a current offlows through a potential difference of.

Electrical power triangle

The electric power triangle is an easy way to memorize the above equation. This formula can be rearranged with the help of an Electrical power triangle shown below.

Electrical Power Electric Power triangle StudySmarterElectrical Power Electric Power triangle, StudySmarter Originals

We can derive the second electrical power formula using Ohm's law. The equation for Ohm's law is given by

We can substitute the value for the potential difference into the equation for power.

or in words

Let us look at a few examples where we calculate power:

Aappliance is supplied by asupply, calculate the power rating of the speaker.

Step 1: List out the given quantities

,

Step 2: Choose the right equation for calculating power

We have the values for current and resistance we can use the following equation

So, the power consumed by the appliance is.

Calculate the potential difference through an electric motor with a current ofand an electric power of.

Step 1: List out the given quantities

Step 2: Choose the right equation for calculating the potential difference

We have the values for current and resistance, we can use the following equation

So the potential difference across the electric motor is.

Calculate the power transferred when a current ofpasses through a conductor of resistance.

Step 1: List out the given quantities

Step 2: Choose the right equation for calculating power

We have the values for current and resistance we can use the following equation

The power is being transmitted is.

Power transmission

For a given value of current, the power consumed increases with an increase in potential difference. The magnitude of power consumed depends on both the current and the potential difference. Therefore electric power can be delivered in the same quantity using different combinations of potential difference and current.

  • Low current with a high voltage
  • High current with a low voltage

Electrical Power High voltage warning StudySmarter Warning signs outside power stations indicate that the voltages present are dangerous to humans and could cause serious harm in the form of an electric shock, StudySmarter

The disadvantage of using a high current with a low potential difference is the heating effect. When large values of current pass through a wire they heat up to high temperatures which reduces the lifetime of the wires. The heating effect is bad as it reduces the efficiency of the electric device. This is because a part of the energy that is being transferred is being converted into heat. For this reason, High powers across the mains are transmitted in high voltages with low currents.

The heating effect is due to the current passing through a resistor. The heat produced is directly proportional to the resistance of the wire or device. When current passes through a conductor it overcomes the resistance of the wire, the work done against the resistance is converted into heat.

Electrical Power - Key takeaways

  • Electric power is defined as the electrical energy transferred in a circuit per unit of time.
  • Electric power or the electric energy transferred in a circuit can be calculated using the electric power formula
  • Electric power can also be calculated using the equation
  • The disadvantage of using a high magnitude of current with a low voltage is the heating effect. When large values of current pass through a wire they heat up to high temperatures which reduces the life of the wires leading to high maintenance costs and wasted energy.
  • High powers across the mains are transmitted in high voltages with low currents.

Frequently Asked Questions about Electrical Power

Electric power is defined as the electrical energy transferred in a circuit per unit of time.

The electric power dissipated in a circuit by a particular component can be calculated using the electric power formula: P=IV, where P is the power, V is the potential difference drop due to the component and I is the current passing through the component.

Electricity is generated in a power station by the combustion of fossil fuels. Water is heated until it reaches boiling temperature. The steam produced turns a turbine which powers a generator which produces electricity.

The SI unit of electric power is the Watt and it is denoted by the symbol W.

Final Electrical Power Quiz

Question

What is the unit for electric power?

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Answer

watt

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Question

What is the equation for power?

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Answer

P=VI

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Question

If the voltage in a circuit is increased the power will ...


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Answer

Increase 

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Question

The power rating tells us the ...

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Answer

Power consumed in 1 second

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Question

Power is directly proportional to the current flowing in the circuit.

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Answer

True

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Question

1 Kilowatt =

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Answer

1000 joules per second

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Question

What is the definition of power?

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Answer

Power is defined as the rate of energy transfer per second

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Question

High voltage or high current, which of these can heat up a wire more?

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Answer

High current

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