Energy Transfers Flashcards

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1
Q

State two equations for the power of a circuit. Give appropriate units.

A

.P= I V
.P=I2 R

Power (watts), Current (Amperes), Potential Difference (Volts), Resistance (Ohms)

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2
Q

State an equation linking energy transferred, power, and time. Give appropriate units.

A

E = P t

Energy (joules), Power (Watts), Time (Seconds)

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3
Q

State an equation linking energy transferred, charge flow and potential difference. Give the appropriate units.

A

.E = QV

Energy (Joules), Charge (Coulombs), Potential Difference (Volts)

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4
Q

What two main factors does the amount of energy transferred by an appliance depend on ?

A

1.How long the appliance is being used for.

2.The power of the appliance.

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5
Q

Describe the energy transfers in a battery powered torch.

A

.Battery converts chemical energy into electrical energy.

.The bulb converts electrical energy into thermal/light energy.

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6
Q

Describe the energy transfers in a battery-powered motor.

A

.Battery converts chemical energy into electrical energy.

.Motor converts electrical energy into kinetic energy as well as waste energy in the form of heating due to friction

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7
Q

What three things determine the power of a circuit device?

A

.The potential difference across the circuit.

.The current through the circuit.

.The amount of energy transferred in a given time.

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8
Q

What is the purpose of the National Grid?

A

.To link power stations to consumers so that they have access to a source of electricity.

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9
Q

What are the two types of transformers used in the National Grid?

A

.1. Step-Up transformers
2.Step-Down transformers

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10
Q

Where are step-up transformers found in the National Grid? What do they do?

A

.Step - Up transformers are used when connecting power stations to transmission cables.

.They increase the potential difference.

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11
Q

Where are step-down transformers found in the National Grid? What do they do?

A

.Step down transformers are used in connecting transmission cables to domestic buildings ( like houses)

.They decrease the potential difference.

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12
Q

Why do transmission lines transfer electricity at high potentials ?

A

.A high potential, results in a low current.

.The lower the current, the less energy that is wasted as heat.

.Therefore, it is more efficient.

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13
Q

Why does the potential difference need to be decreased between transmission lines and houses?

A

.Lower potentials are safer for domestic use and reduces the likelihood of severe electrocution.

.Appliances are designed for 230V.

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