Gr 11 Physical Sciences: Ch 9.2 Power and energy

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What is the unit of measurement for power?

Joule (J)
Ampere (A)
Volt (V)
Watt (W) (correct)

What is the formula for calculating power in an electrical circuit?

P = V · I^2
P = I / V
P = I · V (correct)
P = V / I

What is power directly proportional to?

The square root of the current and voltage
The current and voltage (correct)
The energy and time
The resistance and time

What is the purpose of using Ohm's Law to derive additional power equations?

To provide flexibility in calculating power depending on which quantities are known (A) Signup and view all the answers

What is the formula for power when the voltage across the circuit element and its resistance are known?

P = V^2 / R (C) Signup and view all the answers

What is the formula for power when the current and resistance in the circuit are known?

P = I^2 · R (B) Signup and view all the answers

What is the rate at which electrical energy is converted in an electric circuit?

Power (A) Signup and view all the answers

What is the definition of power?

The rate at which work is done (C) Signup and view all the answers

What is the unit of power in the formula E = P ⋅ t?

Watts (W) (B) Signup and view all the answers

What is the energy consumed by a device with a power rating of 1 kilowatt running for one hour?

1 kWh (D) Signup and view all the answers

To convert power from watts to kilowatts, you should:

Divide by 1000 (B) Signup and view all the answers

What is the formula to calculate the total energy transferred?

E = P ⋅ t (B) Signup and view all the answers

What is the purpose of understanding the principles of electrical power and energy?

To design electrical circuits for efficient use of energy (B) Signup and view all the answers

What is the correct order to find the cost of running an appliance?

<ol> <li>Determine the power rating, 2. Multiply by time, 3. Multiply by cost per kWh (C)</li> </ol> Signup and view all the answers

What is the unit of electrical energy?

Joules (J) (D) Signup and view all the answers

Why is it necessary to multiply the power by the time?

To calculate the total amount of energy transferred (A) Signup and view all the answers

What is the total energy consumed by an electrical device equal to?

The power rating of the device multiplied by the time it is operated. (C) Signup and view all the answers

Why is it necessary to convert time from minutes or seconds to hours for energy consumption calculations?

To make the units consistent with kilowatt-hours. (A) Signup and view all the answers

What is the purpose of calculating the total energy consumption in kilowatt-hours?

To calculate the cost of electricity. (B) Signup and view all the answers

What is the cost of running an appliance dependent on?

The power rating of the appliance, the time it is used, and the cost per kilowatt-hour. (C) Signup and view all the answers

What is the benefit of understanding the principles of electrical power and energy?

It helps in calculating the consumption and costs, and also aids in designing and managing electrical circuits effectively. (D) Signup and view all the answers

How is the cost of electricity calculated?

By multiplying the power rating of the appliance by the time it is used, and then by the cost per kilowatt-hour. (C) Signup and view all the answers

What is the unit of measurement for electrical energy in household and commercial contexts?

Kilowatt-hours (kWh) (D) Signup and view all the answers

What is the formula for calculating the total energy transferred in terms of power and time?

E = P × t (A) Signup and view all the answers

What is the purpose of a battery in an electric circuit?

To convert chemical potential energy into electrical energy (C) Signup and view all the answers

Which of the following is true about the relationship between power and current in an electric circuit?

Power is directly proportional to the square of the current (C) Signup and view all the answers

What happens to the power dissipated or consumed by a circuit if the voltage across the circuit elements increases?

The power increases (D) Signup and view all the answers

Which of the following formulas is useful when the current and resistance in the circuit are known, but the voltage is not?

P = I^2 \cdot R (C) Signup and view all the answers

What is the effect of doubling the voltage across a circuit element on the power consumed by the circuit?

The power increases by a factor of 4 (C) Signup and view all the answers

Which of the following statements is true about electrical power?

Electrical power is a measure of the rate at which work is done (B) Signup and view all the answers

What happens to the power dissipated or consumed by a circuit if the resistance in the circuit increases?

The power increases (D) Signup and view all the answers

Which of the following formulas is useful when the voltage across the circuit element and its resistance are known, but the current is not?

P = V^2 / R (D) Signup and view all the answers

What is the primary function of a battery in an electric circuit?

To convert chemical potential energy into electrical energy (B) Signup and view all the answers

Which of the following statements about power is true?

Power is a measure of the rate at which work is done. (D) Signup and view all the answers

What is the effect of increasing the current flowing through a circuit on the power consumed by the circuit?

The power increases (C) Signup and view all the answers

Which of the following formulas is used to calculate power when the voltage and current are known?

P = I × V (B) Signup and view all the answers

What is the effect of increasing the resistance in a circuit on the power consumed by the circuit?

The power decreases (D) Signup and view all the answers

What is the purpose of deriving alternative formulas for power?

To make the calculation of power more flexible (D) Signup and view all the answers

What is the relationship between power and voltage in an electric circuit?

Power is directly proportional to voltage (B) Signup and view all the answers

What is the unit of power in an electric circuit?

Joules per second (B) Signup and view all the answers

What is the significance of the formula E = P ⋅ t in the context of electrical energy?

It is used to calculate the total energy consumed by an electrical device. (D) Signup and view all the answers

What is the primary motivation for converting power from watts to kilowatts in household and commercial contexts?

To make the energy consumption more relatable to everyday usage. (A) Signup and view all the answers

What is the key factor that determines the cost of electricity?

The cost per kilowatt-hour charged by the electricity provider. (B) Signup and view all the answers

What is the implication of the equation 1 kWh = 1 kW × 1 hour?

It represents the energy consumed by a device with a power rating of 1 kilowatt running for one hour. (C) Signup and view all the answers

What is the benefit of understanding the principles of electrical power and energy in designing and managing electrical circuits?

It aids in the efficient use of energy. (A) Signup and view all the answers

What is the correct sequence of steps to calculate the cost of running an electrical appliance?

Determine the power rating, multiply by time, and multiply by cost per kWh. (B) Signup and view all the answers

What is the significance of the unit kilowatt-hours in the context of electrical energy consumption?

It is a unit of energy. (B) Signup and view all the answers

What is the relationship between the power rating of an electrical appliance and its energy consumption?

The power rating is directly proportional to the energy consumption. (A) Signup and view all the answers