Electrical Current

Electrical current

Amount of charge per unit time

The applied voltage, the material through which the charge flows, and the state of the material

Three things on which the current depends on when the charge flows through a medium.

A large current is present

A large amount of charge is moving through the wire in a small amount of time.

A small current is present

A small amount of charge moves through the circuit over a long period of time.

ampere (A)

The SI unit for the current

I(average) = ΔQ/Δt

Formula to calculate the average current

André-Marie Ampère

The French physicist after whom the SI unit of the current got named.

1 A = 1C/s

Derivation of ampere

Definition of ampere

One Coloumb of charge passing through a given area per second.

Instantaneous electrical current

The time derivative of the charge that flows and is found by taking the limit of the average electrical current as Δt → 0

Also the synonym for what we call electrical current

I = dQ/dt

Mathematical representation of the electrical current

6.25×10^18 electrons

The amount of electrons flowing that cause the current of 1 Ampere in 1 second

τ = RC

Time constant formula for the Resistor-Capacitor circuit

τ = L/R

Time constant formula for the Resistor-Inductor circuit

Qm = C V

Maximum charge on a capacitor formula

Q(t) = Qm(1 - e^-t/τ)

Charge on a capacitor formula

I(t) = (Qm/τ)e^-t/τ

Current on a capacitor formula

Q(t) = Q0*e^-t/τ

Charge on a capacitor formula (discharging)

I(t) = -(Q0/τ)e^-t/τ

Current on a capacitor formula (discharging)

solar cells, 0.30mA

Handheld calculators often use small ___________ to supply the energy. The current needed to run the calculator can be as small as ______.

Circuit breakers

Are used to protect the residents from harm and their appliances from damage due to large currents.

Are rated in amperes, normally in a range from 10amps to 30amps.

Circuit

A complete path for the current to flow from the positive terminal to the negative terminal.

Schematic

A graphical representation of a circuit.

Incandescent

An adjective used for an object that produces light when heated.

A positive terminal

The longer line of a battery schematic is what?

From positive terminal to the negative terminal

The direction of the conventional current

Metal wires

In the material where the current is carried by electron, therefore only negative charges move

In ionic solutions as salt water and also in nerve cells

Where both positive and negative charges move

Van de Graaff generator

Used for nuclear research. Can produce a current of pure positive charges, such as protons

Tevatron Accelerator at Fermilab

The circular particle accelerator that collided beams of protons and antiprotons, due to them traveling in the opposite direction. Was shut down in 2011.

Positive charges

The charges that move in the direction of the electric field. (Electric field’s direction is the same as the direction of the conventional current.)

Negative charges

The charges that move opposite of the direction of the electric field. (Electric field’s direction is the same as the direction of the conventional current.)

Electrical field

______________ is present in conductors and is responsible for producing the current.

Static electrical case

Case where charges in a conductor quickly redistribute themselves on the surface of a conductor in order to cancel out the external electrical field and restore equilibrium.

Battery

The external source of electric potential in an electrical circuit that prevents the charges from ever reaching an equilibrium.

Yes, it is true

Is it true that even though the electrical field is responsible for the motion of the charges in the conductor, but the work done on the charges by the electric field does not increases the kinetic energy of the charges.