Learning Module A1 Flashcards
What does EMF stand for?
Electric Motive Force
What are the five different quantities in electricity?
- Charge
- Current
- Voltage
- Resistance
- Power
These quantities are fundamental in the study of electricity.
What symbol is used to represent the quantity of charge?
Q
Q stands for the quantity of electric charge.
What is the unit of charge represented by the charge on 6.24 x 10^18 electrons?
Coulomb
Named after Charles Augustin Coulomb.
What is the abbreviation for the unit of electric charge?
C
C stands for coulomb.
What does the term ‘current’ refer to in electricity?
The rate of flow of charge
Current is essential for discussing electric circuits.
What symbol is used to represent electric current?
I
The symbol I is likely derived from the word intensity.
What is the unit of current and who is it named after?
Ampere, named after Andre Ampere
The unit is critical for measuring the flow of electric charge.
What is the abbreviation for the unit of current?
A
A stands for ampere.
How is 1 ampere defined in terms of coulombs?
1 A = 1 C/sec
This means 1 coulomb of charge crosses a point in 1 second.
How many electrons correspond to 1 ampere?
6.24 × 10^18 electrons per second
This highlights the large number of electrons constituting a current.
What is needed to move an electron from the negative terminal to the positive terminal?
Voltage
This refers to the energy needed to overcome the forces acting on the electron.
What kind of energy is given to an electron when it is moved against a force?
Potential energy
The energy is given as work is done against the electric forces.
What is the term for the potential energy difference between two points in an electric circuit?
Potential difference
It represents the energy required to move a charge between those points.
What is the abbreviation for potential difference?
PD
What is the unit of potential difference?
Volt
The volt is named after Alessandro Volta.
What is the relationship between joules and coulombs in defining a volt?
1 V = 1 J/C
If it takes 3 joules of energy to move 1 coulomb of charge, what is the potential difference?
3 volts
What happens to potential energy within an energy source and the rest of the circuit?
Potential rise in the source, potential drop in the circuit.
What is the term for the push supplied by the source to the electrons?
Electromotive force (emf)
This push is analogous to compressing a spring.
What is referred to as the voltage drop?
Potential drop occurring in the circuit.
What is the common abbreviation used for both potential difference and electromotive force?
E
What is the abbreviation for resistance?
R
What opposes the flow of electric current in a circuit?
Resistance
Similar to how friction opposes motion.
True or False: If nothing opposed the flow of current, it would eventually stop.
False
What is the electrical unit of resistance?
The ohm
Named after Georg Simon Ohm
What is the abbreviation for the unit of resistance?
The Greek letter omega, 0
How is 1 ohm defined in terms of voltage and current?
1 volt causes a current of 1 ampere to flow
1 Ω = 1 V/A
If 1 volt is applied across a device and ½ of an ampere flows, what is the resistance?
2 ohms
If 3 volts are applied across a device and 1 ampere flows, what is the resistance?
3 ohms
What is the definition of power in physics?
The rate at which work is done or energy is transferred
What is the abbreviation for power?
P
What is the unit of power?
The watt
Who is the watt named after?
James Watt
What is the definition of one watt?
1 joule per second
What is the formula relating power, voltage, and current?
1 W = 1 V x 1 A
What is the definition of energy?
Energy is the ability to do work.
Work is done when an applied force moves an object through a distance in the direction of the applied force.
What is the relationship between work and energy?
When work is done on an object, the object is given energy equal to the work done on it.
The symbol for energy is W, which is also the symbol for work.
In a mechanical sense, how is work defined?
Work is defined as force times distance.
How does an object transfer energy?
An object can transfer energy to another object by doing work on it.
What happens when a force is applied to lift a volume of water?
The volume of water gains energy equal to the work done on it.
What is power?
Power is the rate of doing work.
What is the relationship between energy, power, and time?
Energy = power x time.
In electrical units, how is power calculated?
Power is equal to volts times amperes.
How is energy calculated in electrical units?
Energy is equal to volts times amperes times time.
What do electrical supply authorities charge customers for?
They charge customers for energy, not power.
What type of meter is used to measure energy consumption?
Kilowatt-hour meters.
What is the unit of energy?
The unit of energy is the kilowatt hour.
What is the unit of power?
The unit of power is the watt.
What is the unit of time used in electrical measurements?
The unit of time is the hour.
What is horsepower referring to on a motor?
Output
Input on a motor is defined as?
Power Draw
What is Ohm’s law?
The current in an electric circuit is proportional to the applied voltage and inversely proportional to the resistance of the circuit.
Mathematically, Ohm’s law is expressed as I = E ÷ R.
What is Watt’s law?
The power transformed in an electric circuit is equal to the product of the applied voltage times the circuit current.
Mathematically, Watt’s law is expressed as P = E × I.
How many equations can be derived from Ohm’s law and Watt’s law?
Ten equations can be generated by using transposition and substitution.
These equations allow calculation of any two electrical quantities if the other two are known.
Why is it important to calculate voltage, current, resistance, and power?
It is not always practical or possible to measure all four quantities directly.
Knowing how to calculate them allows for better understanding and troubleshooting of electrical circuits.
What happens to the resistance of a light bulb when it is hot?
The resistance increases
However, when cold, the resistance is significantly lower at about 10 ohms.
What are loads in electrical circuits?
Devices that convert electrical energy to other forms of energy.
Purely resistive devices convert energy mainly to heat, and sometimes to light.
How does current affect the heating of a resistive device?
An increase in current leads to more collisions between electrons and molecules, resulting in increased energy transfer and heating.
This means the device becomes warmer as the rate of electron flow increases.
What is power in the context of electrical circuits?
The rate of doing work or the rate of energy transfer.
Power is directly proportional to both voltage and current.
What happens to power if either voltage or current increases?
Power increases.
This is because power is directly proportional to both voltage and current.
Fill in the blank: Power is directly proportional to both _______ and _______.
voltage, current
What does Ohm’s law state about the relationship between current and voltage?
The current in a circuit is directly proportional to the applied voltage
If the voltage in a circuit doubles, what happens to the current?
The current also doubles
What is the effect on power when both voltage and current double?
The power increases by four times
What is the formula for power in relation to resistance and current?
P = I² x R
What are superconductors?
Conductors that have no resistance
What is I^2 R loss?
Power loss in conductors due to resistance
How is electrical energy converted in a conductor with resistance?
Some electrical energy is converted to heat
What is the formula to calculate IR loss in conductors?
P = I² x R
What could happen if power loss in conductors is reduced?
Fewer generating stations would be needed, reducing pollution