Electric Circuits and Laws of Electricity

For an electric current to flow through a wire, there must be a complete circuit, a potential difference (voltage) across the circuit, and a material that allows electrons to flow freely.
Kirchhoff's first law (Kirchhoff's Current Law) states that the total current entering a junction must equal the total current leaving the junction.

Magnetic field lines extend from the north pole of a magnet to the south pole and form closed loops.

In a series circuit, all components are connected in a single loop.
A series circuit is used in simple applications where only one path for current flow is required, such as a string of Christmas lights.
In a series circuit, if one globe is blown, the entire circuit breaks, and all globes go out.

In a parallel circuit, each component has its own separate path for current flow.
Parallel circuits are used in applications where individual components can be turned on or off independently, such as the electrical wiring in a house.
In a parallel circuit, if one globe is blown, the other globes will remain lit.

The voltage across a circuit can be calculated using Ohm's law: V = I * R.
Where V is the voltage (in volts), I is the current (in amps), and R is the resistance (in ohms).
The resistance of a circuit can be calculated by rearranging Ohm's Law into: R = V / I.

A fuse is a safety device designed to break a circuit if there is an excessive amount of current flowing through it.
This prevents the wires from overheating and potentially causing a fire.

Static electricity refers to an imbalance of electrical charges on the surface of a material.
This happens when there is a transfer of electrons between two objects, leaving one object with a positive charge and the other with a negative charge.
A Van der Graf generator creates static electricity by transferring electrons from a belt to a spherical conductor. The build-up of charges on the sphere creates a high voltage, which can be used for demonstrations.

The Doppler effect describes the change in frequency of a wave observed by a detector moving relative to the source of the wave.
For example, the pitch of a siren sounds higher as it approaches and lower as it moves away. This is because the waves are compressed in front of the siren and stretched out behind it.

An electric motor uses the interaction between a magnetic field and an electric current to produce rotation.
A coil of wire, known as an armature, is placed in a magnetic field. When an electric current flows through the coil, it creates a magnetic field that interacts with the external magnetic field. This interaction results in a force that causes the armature to rotate.

An electromagnet is a coil of wire that produces a magnetic field when an electric current flows through it.
The strength of the magnetic field is proportional to the current flowing through the coil and the number of turns in the coil.
The direction of the magnetic field can be reversed by reversing the direction of the current flow through the coil.

For a current to flow through a wire, there must be a closed circuit and a potential difference (voltage) across the wire.
Kirchhoff's first law states that the total current entering a junction in a circuit is equal to the total current leaving the junction.

Magnetic fields are created by moving electric charges.
The magnetic field lines around a bar magnet point from the north pole to the south pole. These lines never cross.

In a parallel circuit, components are connected across each other.
The voltage across each component in a parallel circuit is the same.
If one component in a parallel circuit fails, the other components will continue to function.

Series circuits are often used in simple circuits, like a string of Christmas lights, since there is only one path for current to flow.
Parallel circuits are commonly used in household wiring because if one appliance fails, the others can continue to work.
Globes in a series circuit will be dimmer than globes in a parallel circuit.
In a series circuit, if one globe is blown, the entire circuit will be broken. In a parallel circuit, if one globe is blown, the other globes will continue to function.
A parallel circuit will drain the battery quicker because the current has multiple paths to flow through, creating a greater total current.

Ohm's law states that the voltage (V) across a conductor is directly proportional to the current (I) through it, provided the temperature remains constant.
The constant of proportionality is known as the resistance (R).

A fuse is a safety device that prevents excessive current from flowing through a circuit.
A fuse is designed to melt and break the circuit if the current exceeds a certain limit.

Static electricity is the accumulation of electric charge on a surface.
This can happen when different materials are rubbed together and electrons are transferred from one material to another.
There is no flow of current in static electricity - just a separation of charge.
A Van Der Graaf generator works by creating a static charge on a metal dome. The charge builds up until it is released in a spark.
The Van Der Graaf uses a moving belt to transfer electrons onto a metal dome.

The Doppler effect is the change in frequency of a wave (such as sound or light) that occurs when the source of the wave is moving relative to the observer.
If the source is moving towards the observer, the frequency of the wave is increased, leading to a higher pitch sound or a blue shift in light.
If the source is moving away from the observer, the frequency of the wave is decreased, leading to a lower pitch sound or a red shift in light.
An example of the Doppler effect is the change in pitch of a siren as an ambulance approaches and then moves away from you.

An electric motor converts electrical energy into mechanical energy.
It uses a magnetic field to rotate a coil of wire carrying an electric current.
The coil is placed in a magnetic field, and when current flows through the coil, it experiences a force that causes it to rotate.

An electromagnet is a temporary magnet created by wrapping a wire coil around a core of iron.
When an electric current flows through the coil, a magnetic field is produced in the core.
The strength of the electromagnet increases as the number of loops in the coil increases and/or the current flowing through it increases.
The magnetic field ceases to exist when the electric current is turned off.