Electricity 1: current, charge, p.d, EMF, resistance, ohms law, IV characteristics, resistivity

Electric current definition

Rate of net flow of any electrically charged particles

Conventional current definition and what is different With how electrons flow

The direction in which a unit positive charge would go from; positive to negative terminal

Electrons flow from negative to positive terminals, they move at random but with the Electromotor force, it makes the electrons move in the same direction

What is the definition of a coulomb?

Different equations for charge and this units

What does ‘e’ and ‘n’ stand for

Equal to the charge passes when a current of one ampere flows for one second

Q=It

ne=It

C=As

‘e’= elementary charge = (-)1.6×10^-19

‘n’= number of electrons or protons

What is the difference between flow in an electrical current through a metal or through electrolytes?

Electric current through a metal is due to the flow of electrons however electric current through electrolytes is due to flow of irons

How are ions attracted?

Irons are attracted to their opposite charge terminals

Positive ions are attracted to the anode

Negative ions are attracted to the cathode

What is the charge of 1mAh

(1×10^-3)(3600)=3.6 C

Times by 3.6

What is the definition for potential difference And voltmeter( and explain the voltmeter characteristic)

Energy transferred per unit charge, transferred from electrical to other forms

Measures potential difference across two points in a circuit. Vote meter has infinity resistance and is connected in parallel across the component.

Definition of volts

Equations for potential difference in its units

Boats are the potential difference between two points when 1 joule of work is done to move a charge of 1 coulomb

V=W/Q

V=IR

Volts=JC^-1

How do you calculate the electrical potential energy?

How do you calculate the electrical potential injury for a single electron?

W=QV=ItV

W=eV

Q=e

Definition for resistance, its equation and its unit equivalent

Ratio of the potential difference across the resistor to the current through it

R=V/I

Ohms=VA^-1

(This is not ohms law)

What is the definition for ohms law?

For metallic conductor (not all), Potential difference across is directly proportional to The current through it when other physical conditions such as temperature is constant

I-V and V-I are completely different, state why and state the equation = to the gradient equation

The first letter is always the X axis and the second letter is always the Y axis

For IV, steep means it has a low resistance

V=IR

y=xm+c

For VI, steep means it has a high resistance

I=(1/R)V

y=mx+c

Show and explain the VI graph of an ohmic resistor

Show and explain the VI graph of a filament lamp that is non-ohmic

VI is constant as it is directly proportional therefore the resistance is constant

VI increases, therefore the resistance increases

Show and explain the VI graph for semiconductor NTC thermistor (non-ohmic)

Show and explain the VI graph for a semiconductor diode (non-ohmic)

VI decreases, therefore the resistance decreases

V0=1.4v for an LED

If the volts are less than V0, the current is 0/very small so it has a high resistance

If the volts are greater, VI decreases therefore resistance decreases

What are causes of electrical resistance

Current throw component has a heating effect therefore if temperature increases, the ions will vibrate more

This means that the rate of electron-ion collisions increase and therefore the resistance increases

Full resistance how can you increase or decrease resistance?

Since resistance is directly proportional to length, If you increase the length, you increase the resistance and if you decrease the length, you decrease the resistance

Resistance is also inversely proportional to the diameter so if you increase the diameter you decrease the resistance and if you decrease the diameter, you increase the resistance

What is the equation for resistivity and its unit?

Row=RA/l

Resistivity = resistance x Cross-sectional area/Length

Ohms m

What is resistivity independent or dependent on?

Resistivity is independent to dimensions so no matter how much of a material you have it won’t affect it

Resistivity is dependent on the temperature of the material

Show and explain the temperature resistance graph for metallic conductor

Show and explain the temperature resistance graph for semiconductor NTC

increase in temperature = increase in resistance. This is because irons are more which means more kinetic energy which means the rate of electron-ion collisions increase

An increase in temperature = decrease and resistance therefore resistivity decreases and more charge carriers become available ( delocalise)

Show and explain the temperature resistance graph for a superconductor

Anything less than the critical temperature the resistance equals zero

Why are superconductors used?

Superconductors allow large currents to flow without the loss of thermal energy and also create a large magnetic field

These are used to improve efficiency of electrical productions such as Transformers generators and transmission lines

Due to the large magnetic fields, they can also be used as electromagnets to produce fields Such as MRI scanners and particle accelerators