Power MCQ Quiz - Objective Question with Answer for Power - Download Free PDF

The correct answer is I × V.

Key Points

• The power $P$ in an electrical circuit is calculated using the formula P=I×V" id="MathJax-Element-2-Frame" role="presentation" style="position: relative;" tabindex="0">P=I×V P=I×V $P = I \times V$ , where $I$ is the current and $V$ is the voltage.
• This formula represents the rate at which electrical energy is converted into another form of energy.
• The unit of power is the watt (W), where 1 watt is equal to 1 ampere of current flowing through a potential difference of 1 volt.
• This relationship is derived from Ohm's Law and the definition of power in physics.

Additional Information

• Ohm's Law
  • Ohm's Law states that V=I×R" id="MathJax-Element-5-Frame" role="presentation" style="position: relative;" tabindex="0">V=I×R V=I×R $V = I \times R$ , where $V$ is the voltage, $I$ is the current, and $R$ is the resistance.
  • This fundamental principle is crucial for analyzing electrical circuits.
• Watt
  • The watt (W) is the SI unit of power.
  • It is defined as one joule per second.
• Electrical Energy
  • Electrical energy is the energy derived from electric potential energy or kinetic energy.
  • It is used to power various devices and systems.
• Power in Resistive Circuits
  • In purely resistive circuits, the power dissipated is purely due to resistance.
  • The power formula P=I2×R" id="MathJax-Element-9-Frame" role="presentation" style="position: relative;" tabindex="0">P=I2×R P=I2×R $P = I^2 \times R$ can also be used in such cases.

The Correct answer is 1 kW = 1000 J/s.

Key Points

• The unit kilowatt (kW) is a measure of power in the International System of Units (SI).
• 1 kilowatt is equivalent to 1000 watts (W), where 1 watt is defined as 1 joule per second (1 W = 1 J/s).
• Thus, 1 kW = 1000 J/s, which means that 1 kilowatt represents the transfer of 1000 joules of energy per second.
• This relationship is derived from the basic definition of power, which is the rate of doing work or transferring energy.
• The unit kilowatt is commonly used in various applications, including electricity billing, mechanical systems, and energy consumption measurements.
• For example, the power rating of household appliances like air conditioners, heaters, and washing machines is often given in kilowatts.
• This conversion is fundamental in understanding the energy consumption and efficiency of devices, making it essential for calculations in physics and engineering.

 Additional Information

• 10 J/s
  • This is a smaller unit of power and does not equate to 1 kilowatt. It is equivalent to 10 watts, which is significantly less than 1 kW.
• 100 J/s
  • While closer in value, this is still much smaller than 1 kilowatt. It represents 100 watts, which is one-tenth of a kilowatt.
• 1 J/s
  • This is the definition of 1 watt, the basic unit of power in the SI system. However, it is far smaller than 1 kilowatt, as it is only one-thousandth of a kilowatt.

The Correct answer is P = VI.

Key Points

• The formula P = VI is the fundamental expression for calculating electric power in a circuit.
• Power (P) in an electrical circuit represents the rate at which electrical energy is transferred or converted into another form of energy, such as heat or light.
• The formula indicates that power is the product of voltage (V) and current (I), where:
  • Voltage (V) is the potential difference across two points in the circuit, measured in volts.
  • Current (I) is the flow of electric charge through a conductor, measured in amperes.
• This formula is derived from the basic definition of power: Power = Work / Time. In the context of electricity, work is the product of charge and potential difference, and dividing it by time leads to the formula P = VI.
• It is a widely used formula in analyzing electrical circuits, determining the efficiency of devices, and calculating energy consumption.
• This relationship is valid for both direct current (DC) and alternating current (AC) circuits, though in AC circuits, factors such as phase difference and power factor may need to be considered.
• For example, if the voltage across a circuit is 10 volts and the current is 2 amperes, the power is calculated as:
  • P = VI = 10 × 2 = 20 watts

 Additional Information

• P = V/I
  • This formula is incorrect because dividing voltage by current gives resistance (R), not power.
  • The relationship is derived from Ohm's Law, which states that V = IR, where R is resistance.
• P = V²I
  • This formula is incorrect and does not follow the principles of power calculation. It appears to be a misrepresentation of the power equation.
• P = V²/I
  • This formula is also incorrect. It is not consistent with the physical laws governing electrical circuits.

The correct answer is 300 W.

Key Points

• The formula for calculating Power is given by:
  Power = Work Done / Time.
• Work done is calculated using the formula:
  Work Done = Force × Distance.
• Here, the force is equal to the weight of the boy, which is 600 N, and the distance climbed is 10 m.
• Substituting the values into the formula for work done:
  Work Done = 600 N × 10 m = 6000 J (Joules).
• The time taken by the boy to climb is 20 seconds.
• Now, substitute the work done and time into the power formula:
  Power = 6000 J / 20 s = 300 W (Watts).
• Therefore, the power expended by the boy is 300 W.

 Additional Information

• Power
  • Power is the rate at which work is done or energy is transferred over time.
  • The SI unit of power is the Watt, which is equivalent to one Joule per second.
  • Power is a scalar quantity and is crucial for understanding the efficiency of machines and systems.
• Work Done
  • Work Done is the energy transferred when a force is applied over a distance in the direction of the force.
  • The SI unit of work is the Joule, and it is calculated as:
    Work Done = Force × Distance × cos(θ), where θ is the angle between force and displacement.
• Force
  • Force is an interaction that changes the motion of an object or causes it to deform.
  • It is measured in Newtons (N), and 1 Newton is defined as the force required to accelerate a 1 kg mass by 1 m/s².

The Correct answer is Power.

Key Points

• Power is defined as the rate at which work is done or energy is transferred.
• It is mathematically expressed as Power = Work Done / Time.
• The unit of power in the SI system is the watt (W), where 1 watt equals 1 joule per second.
• In the context of machines, power measures how quickly the machine performs work.
• A machine with a higher power rating can accomplish the same amount of work in less time compared to a machine with a lower power rating.
• The concept of power is critical in fields like engineering, physics, and energy management, where efficiency and performance are essential.
• Examples of power in machines include the horsepower rating of engines or the kilowatt rating of electrical devices.

 Additional Information

• Total energy consumed
  • Total energy consumed refers to the overall amount of energy used by a machine or system during its operation.
  • While total energy is an important concept, it does not measure how quickly the work is done, which is why it does not determine the rate of work performed.
• Rate of change of velocity
  • The rate of change of velocity is known as acceleration.
  • Although acceleration is a key concept in physics, it does not directly measure the rate of work performed by a machine.
  • Acceleration is more relevant to the study of motion rather than energy transfer or work done.
• Total force exerted
  • Total force exerted refers to the overall force applied by or on a machine.
  • Force is a component of work, but it does not account for the time factor, which is crucial in determining the rate of work.
  • For example, a large force applied over a long duration might result in less power than a smaller force applied quickly.

The correct answer is I × V.

Key Points

• The power $P$ in an electrical circuit is calculated using the formula P=I×V" id="MathJax-Element-2-Frame" role="presentation" style="position: relative;" tabindex="0">P=I×V P=I×V $P = I \times V$ , where $I$ is the current and $V$ is the voltage.
• This formula represents the rate at which electrical energy is converted into another form of energy.
• The unit of power is the watt (W), where 1 watt is equal to 1 ampere of current flowing through a potential difference of 1 volt.
• This relationship is derived from Ohm's Law and the definition of power in physics.

Additional Information

• Ohm's Law
  • Ohm's Law states that V=I×R" id="MathJax-Element-5-Frame" role="presentation" style="position: relative;" tabindex="0">V=I×R V=I×R $V = I \times R$ , where $V$ is the voltage, $I$ is the current, and $R$ is the resistance.
  • This fundamental principle is crucial for analyzing electrical circuits.
• Watt
  • The watt (W) is the SI unit of power.
  • It is defined as one joule per second.
• Electrical Energy
  • Electrical energy is the energy derived from electric potential energy or kinetic energy.
  • It is used to power various devices and systems.
• Power in Resistive Circuits
  • In purely resistive circuits, the power dissipated is purely due to resistance.
  • The power formula P=I2×R" id="MathJax-Element-9-Frame" role="presentation" style="position: relative;" tabindex="0">P=I2×R P=I2×R $P = I^2 \times R$ can also be used in such cases.

The Correct answer is 1 kW = 1000 J/s.

Key Points

• The unit kilowatt (kW) is a measure of power in the International System of Units (SI).
• 1 kilowatt is equivalent to 1000 watts (W), where 1 watt is defined as 1 joule per second (1 W = 1 J/s).
• Thus, 1 kW = 1000 J/s, which means that 1 kilowatt represents the transfer of 1000 joules of energy per second.
• This relationship is derived from the basic definition of power, which is the rate of doing work or transferring energy.
• The unit kilowatt is commonly used in various applications, including electricity billing, mechanical systems, and energy consumption measurements.
• For example, the power rating of household appliances like air conditioners, heaters, and washing machines is often given in kilowatts.
• This conversion is fundamental in understanding the energy consumption and efficiency of devices, making it essential for calculations in physics and engineering.

 Additional Information

• 10 J/s
  • This is a smaller unit of power and does not equate to 1 kilowatt. It is equivalent to 10 watts, which is significantly less than 1 kW.
• 100 J/s
  • While closer in value, this is still much smaller than 1 kilowatt. It represents 100 watts, which is one-tenth of a kilowatt.
• 1 J/s
  • This is the definition of 1 watt, the basic unit of power in the SI system. However, it is far smaller than 1 kilowatt, as it is only one-thousandth of a kilowatt.

The Correct answer is P = VI.

Key Points

• The formula P = VI is the fundamental expression for calculating electric power in a circuit.
• Power (P) in an electrical circuit represents the rate at which electrical energy is transferred or converted into another form of energy, such as heat or light.
• The formula indicates that power is the product of voltage (V) and current (I), where:
  • Voltage (V) is the potential difference across two points in the circuit, measured in volts.
  • Current (I) is the flow of electric charge through a conductor, measured in amperes.
• This formula is derived from the basic definition of power: Power = Work / Time. In the context of electricity, work is the product of charge and potential difference, and dividing it by time leads to the formula P = VI.
• It is a widely used formula in analyzing electrical circuits, determining the efficiency of devices, and calculating energy consumption.
• This relationship is valid for both direct current (DC) and alternating current (AC) circuits, though in AC circuits, factors such as phase difference and power factor may need to be considered.
• For example, if the voltage across a circuit is 10 volts and the current is 2 amperes, the power is calculated as:
  • P = VI = 10 × 2 = 20 watts

 Additional Information

• P = V/I
  • This formula is incorrect because dividing voltage by current gives resistance (R), not power.
  • The relationship is derived from Ohm's Law, which states that V = IR, where R is resistance.
• P = V²I
  • This formula is incorrect and does not follow the principles of power calculation. It appears to be a misrepresentation of the power equation.
• P = V²/I
  • This formula is also incorrect. It is not consistent with the physical laws governing electrical circuits.

The correct answer is 300 W.

Key Points

• The formula for calculating Power is given by:
  Power = Work Done / Time.
• Work done is calculated using the formula:
  Work Done = Force × Distance.
• Here, the force is equal to the weight of the boy, which is 600 N, and the distance climbed is 10 m.
• Substituting the values into the formula for work done:
  Work Done = 600 N × 10 m = 6000 J (Joules).
• The time taken by the boy to climb is 20 seconds.
• Now, substitute the work done and time into the power formula:
  Power = 6000 J / 20 s = 300 W (Watts).
• Therefore, the power expended by the boy is 300 W.

 Additional Information

• Power
  • Power is the rate at which work is done or energy is transferred over time.
  • The SI unit of power is the Watt, which is equivalent to one Joule per second.
  • Power is a scalar quantity and is crucial for understanding the efficiency of machines and systems.
• Work Done
  • Work Done is the energy transferred when a force is applied over a distance in the direction of the force.
  • The SI unit of work is the Joule, and it is calculated as:
    Work Done = Force × Distance × cos(θ), where θ is the angle between force and displacement.
• Force
  • Force is an interaction that changes the motion of an object or causes it to deform.
  • It is measured in Newtons (N), and 1 Newton is defined as the force required to accelerate a 1 kg mass by 1 m/s².

The Correct answer is Power.

Key Points

• Power is defined as the rate at which work is done or energy is transferred.
• It is mathematically expressed as Power = Work Done / Time.
• The unit of power in the SI system is the watt (W), where 1 watt equals 1 joule per second.
• In the context of machines, power measures how quickly the machine performs work.
• A machine with a higher power rating can accomplish the same amount of work in less time compared to a machine with a lower power rating.
• The concept of power is critical in fields like engineering, physics, and energy management, where efficiency and performance are essential.
• Examples of power in machines include the horsepower rating of engines or the kilowatt rating of electrical devices.

 Additional Information

• Total energy consumed
  • Total energy consumed refers to the overall amount of energy used by a machine or system during its operation.
  • While total energy is an important concept, it does not measure how quickly the work is done, which is why it does not determine the rate of work performed.
• Rate of change of velocity
  • The rate of change of velocity is known as acceleration.
  • Although acceleration is a key concept in physics, it does not directly measure the rate of work performed by a machine.
  • Acceleration is more relevant to the study of motion rather than energy transfer or work done.
• Total force exerted
  • Total force exerted refers to the overall force applied by or on a machine.
  • Force is a component of work, but it does not account for the time factor, which is crucial in determining the rate of work.
  • For example, a large force applied over a long duration might result in less power than a smaller force applied quickly.

The correct answer is 315 W.

Key Points

• The power rating of a device can be calculated using the formula P = V x I, where P is power, V is voltage, and I is current.
• Given the current (I) is 1.75 A and the voltage (V) is 180 V.
• Using the formula: P = 180 V x 1.75 A.
• Therefore, the power rating (P) = 315 W.

Additional Information

• Power (P): The rate at which electrical energy is transferred by an electric circuit, measured in watts (W).
• Voltage (V): The electrical potential difference between two points, measured in volts (V).
• Current (I): The flow of electric charge through a conductor, measured in amperes (A).
• Ohm's Law: The relationship between voltage, current, and resistance in an electric circuit, expressed as V = I x R.
• Electric Power Formula: The formula to calculate electric power is P = V x I, where P is power, V is voltage, and I is current.

The correct answer is I × V.

Key Points

• The power $P$ in an electrical circuit is calculated using the formula, \(P=IV\), where I is the current and V is the voltage.
• This formula represents the rate at which electrical energy is converted into another form of energy.
• The unit of power is the watt (W), where 1 watt is equal to 1 ampere of current flowing through a potential difference of 1 volt.
• This relationship is derived from Ohm's Law and the definition of power in physics.

Additional Information

• Ohm's Law
  • Ohm's Law states that, \(V=IR\) where V is the voltage, I is the current, and R is the resistance.
  • This fundamental principle is crucial for analyzing electrical circuits.
• Watt
  • The watt (W) is the SI unit of power.
  • It is defined as one joule per second.
• Electrical Energy
  • Electrical energy is the energy derived from electric potential energy or kinetic energy.
  • It is used to power various devices and systems.
• Power in Resistive Circuits
  • In purely resistive circuits, the power dissipated is purely due to resistance.
  • The power formula \(P=I^2R\) can also be used in such cases.