Work, Energy, Power Concepts
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Questions and Answers

Define the term mass.

It is the measure of the amount of substance contained by an object.

State the unit of measurement of mass.

Kilograms, symbol is kg.

Define the term force.

It is the push or pull required to change the motion of an object.

What is the unit of measurement of force?

<p>Newtons, symbol is N.</p> Signup and view all the answers

Define the term weight.

<p>It is a measurement of the force required to equal the force of gravity that exists between two masses.</p> Signup and view all the answers

At sea level, an object that has a mass of 1 kg exerts a force of (or weighs) about ___.

<p>9.81 N</p> Signup and view all the answers

What is the unit of measurement of weight?

<p>Newtons, symbol is N.</p> Signup and view all the answers

List three other forces besides gravity.

<p>Electromagnetic force, strong nuclear force, weak nuclear force.</p> Signup and view all the answers

Define electromagnetic force.

<p>The force between two electrical charges.</p> Signup and view all the answers

Define strong nuclear force.

<p>The force that holds the protons and neutrons in the nucleus of an atom.</p> Signup and view all the answers

Define weak nuclear force.

<p>The force between subatomic particles.</p> Signup and view all the answers

Gravity is a factor in the ___ of an object.

<p>weight</p> Signup and view all the answers

State the difference between mass and weight.

<p>Mass is constant, but weight varies according to the strength of the gravitational pull.</p> Signup and view all the answers

Define the term work.

<p>It is the application of a force to an object to change its motion. Work is measured in joules (J).</p> Signup and view all the answers

Define the term energy.

<p>It is the ability to do work. The unit of measurement is joules, symbol is J.</p> Signup and view all the answers

Define the term power.

<p>It is the rate of doing work. The symbol for power is P.</p> Signup and view all the answers

What is the unit of measurement for power?

<p>Watt, symbol is W.</p> Signup and view all the answers

A charged battery contains:

<p>energy.</p> Signup and view all the answers

The rate of doing work is expressed in:

<p>watts.</p> Signup and view all the answers

Energy exists in two basic forms. They are:

<p>Kinetic energy, potential energy.</p> Signup and view all the answers

Define the term joule.

<p>The energy required to cause a force of one newton to act through a distance of 1 m.</p> Signup and view all the answers

What is the formula for work?

<p>W = f * d</p> Signup and view all the answers

What is the electrical and mechanical energy formula?

<p>J = C * V</p> Signup and view all the answers

What is the power equation formula?

<p>P = e/t</p> Signup and view all the answers

What is the electrical power formula?

<p>P = V * I</p> Signup and view all the answers

What is the electrical power formula if the resistance and current are known?

<p>P = I^2 * R</p> Signup and view all the answers

What is the electrical power formula if the voltage and resistance are known?

<p>P = V^2 / R</p> Signup and view all the answers

What is the approximate relationship of horsepower to watts?

<p>1 hp = 746 W or 0.746 kW.</p> Signup and view all the answers

What is the electrical energy measurement formula?

<p>Power = energy / time; Energy = power * time.</p> Signup and view all the answers

Electrical energy is measured by a unit called ___.

<p>kilowatt-hour (kWh).</p> Signup and view all the answers

What is the amount of energy used formula?

<p>W = P * t</p> Signup and view all the answers

To find the energy consumed:

<p>Energy = P * time.</p> Signup and view all the answers

To find the energy used in megajoules:

<p>Multiply the number of kilowatt-hours by 3.6.</p> Signup and view all the answers

To find line and motor loss:

<p>P = I^2 * R.</p> Signup and view all the answers

What is the efficiency of the circuit formula?

<p>%Efficiency = Pout / (Pout + Ploss) * 100.</p> Signup and view all the answers

Accounting for conductor resistance, how are most loads hooked up in the field?

<p>Series-parallel.</p> Signup and view all the answers

List three types of losses that must be factored in when considering the efficiency of a motor circuit.

<p>Windage, core losses, and friction.</p> Signup and view all the answers

The symbol used in a formula to represent the rate of energy dissipation in an electric circuit is P.

<p>False</p> Signup and view all the answers

Electric energy is equal to:

<p>power multiplied by time.</p> Signup and view all the answers

An instrument that measures the power dissipated by a circuit must measure:

<p>current and voltage.</p> Signup and view all the answers

The force due to gravity is called weight.

<p>False</p> Signup and view all the answers

One watt-second is called a joule. Therefore, 1 kWh is equal to:

<p>1000 watts times 3600 seconds.</p> Signup and view all the answers

The symbol used to represent electrical power is:

<p>P.</p> Signup and view all the answers

The SI symbol used to represent the unit of measurement for power in an electric circuit is P.

<p>False</p> Signup and view all the answers

Study Notes

Key Definitions

  • Mass: Measure of substance in an object; expressed in kilograms (kg).
  • Force: Push or pull needed to alter an object's motion; measured in newtons (N).
  • Weight: Force of gravity acting on a mass; varies with gravitational pull, measured in newtons (N).
  • Work: Application of force to change motion; measured in joules (J).
  • Energy: Ability to perform work; also measured in joules (J).
  • Power: Rate of doing work; symbolized as P and measured in watts (W).

Forces and Their Types

  • Electromagnetic Force: Force between two electrical charges.
  • Strong Nuclear Force: Holds protons and neutrons in an atom's nucleus, overcoming repulsion.
  • Weak Nuclear Force: Acts between subatomic particles.

Key Equations

  • Work Formula: W = f * d (where f = force, d = distance).
  • Power Equation: P = e / t (power in watts, energy in joules, time in seconds).
  • Electrical Power Formula: P = V * I (power in watts, voltage in volts, current in amperes).
  • Efficiency Formula: %Efficiency = Pout / (Pout + Ploss) * 100.

Energy Forms and Measurements

  • Kinetic Energy: Energy of motion.
  • Potential Energy: Energy due to an object's position.
  • Electrical Energy Measurement: kWh; calculated based on power and time (1 kWh = 3600 kJ).

Efficiency Considerations

  • Common types of losses in motor circuits: windage, core losses, and friction.
  • Line and Motor Loss Formula: P = I^2 * R.

Conversion Facts

  • Energy used in megajoules: Multiply kWh by 3.6.
  • Horsepower to watts conversion: 1 hp = 746 W (0.746 kW).

Measurement Instruments

  • To assess power in a circuit, both current and voltage must be measured.

Common Misconceptions

  • Weight is indeed the force due to gravity.
  • One watt-second equals a joule, thus 1 kWh equates to 1000 watts times 3600 seconds.

Miscellaneous

  • Series-parallel: Configuration used to offset conductor resistance in loads.
  • Power Symbol: Represented by P in formulas, but SI unit for electric power is not symbolized as P.

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Explore key concepts related to work, energy, power, and efficiency with this flashcard quiz. Test your knowledge on fundamental terms such as mass, force, and their measurements. Ideal for students looking to strengthen their understanding of physics.

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