What is electrical current (I) ?

The amount of charge (Q) that flows past a point in a given amount of time (t)

What are the units of electrical current ?

Amps (amperes)

OR

Coulombs/second

How is an electrical current caused ?

By the movement of electrons between two points of significant potential difference of an electrical circuit.

How is energy lost by an electrical circuit ?

Free electrons accelerate towards the positive connection. As they move, they collide with atoms in the substance, losing energy which we observe as heat.

What is an electric current ?

The motion of electrons

What happens to an electrical circuit if the magnitude of the electric potential is increased ?

The current will increase because the electrons will accelerate faster

Describe the concept of joule heating ?

Collisions between electrons and atoms transfer energy to the atoms, which is released as heat.

What are Ohmic conductors ?

Materials such as joule heaters that obey Ohm's law, V=IR

What is Ohm's law ?

Describe how Ohm's law works ?

What is an Ammeter ?

Used to measure the flow of current

What is this ?

An ammeter - measures the flow of current

What is resistance (R) ?

The measure of opposition to the flow of electrons in a substance

What is resistivity (p) ?

The inherent resistive property of a substance, which varies with temperature

What is the equation that includes resistance and resistivity ?

Why does electrical resistance vary with temperature ?

The thermal motion of molecules increases with temperature, resulting in more collisions between electrons which impede their flow.

What are the units of resistance ?

Ohm's

1 Ohm = 1 volt/ampere

What happens when a positive current flows across a resistor ?

There is a voltage decrease and a power loss.

P = VI = V^{2}/R

Describe how to calculate electrical power ?

What does a resistor look like in a circuit diagram ?

What is this ?

A bulb.

(N.B. This also acts like a resistor!)

Why is a bulb in an electrical circuit treated like a resistor ?

The filament inside a light bulb resists the flow of current, and becomes bright and hot.

The brightness of the bulb depends on how much power it loses.

What are the units of Q (charge) ?

Coulombs (C)

What are Capacitors ?

They are used in circuits to store charge, they are similar to batteries but can discharge much more quickly.

E.g. A flash gun on a camera

What is the unit of a capacitor ?

Farad

Describe what is meant by a series circuit ?

One component follows another...

How would you calculate the resistance of two resistors in series ?

R_{total} = R_{1} + R_{2} etc...

Describe what is meant by a parallel circuit ?

How would you calculate the resistance of two resistors in parallel ?

1/R_{total }= 1/R_{1} + 1/R_{2}

What does EMF stand for ?

Electromotive Force

E.g. A battery

Units: Volts

Symbol: