physics mghs26

what is dc current

direct current (DC) electricity flows in one direction and is constant.

what is ac current

alternating current (AC) electricity flows in two directions and changes over time, like a wave

what are the components of a dry cell battery

cells, electrodes, paste

cell dc

a true battery links multiple cells in series, though everyday language calls a single cell a battery

electrodes dc

each cell contains a positive carbon rod terminal and a negative zinc case terminal

paste dc

general-purpose cells use a chemical paste electrolyte rather than a liquid, classifying them as dry cells

how does a dry cell battery work

connection: a closed circuit creates a conducting path between terminals.

reaction: chemicals react between the paste and the zinc case.

flow: this internal chemical reaction releases electric charge to create a current.

storage: a separating layer blocks chemical reactions when the cell is idle.

what are some examples of dc batteries?

alkaline cells: strong current; great for torches and cameras.

mercury cells: steady voltage; good for hearing aids and calculators.

car batteries: lead and acid parts; rechargeable until lead sulfate builds up.

nickel-cadmium cells: rechargeable phone batteries; includes lithium types too

definition of a dry cell?

a battery type with a paste electrolyte

definition of a photovoltaic cell

convert sunlight into electrical energy by freeing electrons to flow through a circuit

definition of electrolyte

substance that allows electric charge to flow

definition of electrode

a conductor through which electricity enters or leaves a cell

how do photovoltaic cells work

sunlight particles, called photons, strike the solar cell surface and enter the semiconductor. electrons are dislodged and forced to move creating a direct current. excess energy can be stores for low light periods,and cells connect to form modules (solar panels), and multiple modules wire together into arrays. only ab 20% of solar energy is converted into electricity

what does generation of electricity by power plants depend on?

magnetism and electricity

definition of magnetism

the force of attraction or repulsion between magnets

definition of a magnetic field

the region around a magnet that determines the strength and direction of their force on other magnets

how was the first electric generator made

electric current by moving a coil of wire through a magnetic field

what are the most common magnetic materials?

iron, nickel, and cobalt

what causes the most magnetic materials to be so magnetic?

their electrons have a special configuration around their nucleus which allows them to all orient themselves in the same direction when they are subjected to an external magnetic field, causing the small magnetic fields to turn into a larger magnetic field

what are the properties of magnets

all magnets, regardless of shape or size, have a south pole and a north pole. opposite poles attract while like poles repel

what is a permanent magnet

a magnet that retains its magnetism at all times

what is a temporary magnet

lose their magnetism when removed from other magnets (eg. a nail suspended from a permanent magnet) or when an electric current is no longer supplied (eg. electromagnets)

what direction are magnetic field lines directed

away from the north pole and towards the south pole; closer the lines, the stronger the field

what is an electromagnet

electromagnet is a temporary magnet consisting of a coil of wire and often an iron core. the coil of wire is called a solenoid

what does a electromagnet consist of

a coil of wire(solenoid) and often an iron core

what is the coil of wire in an electromagnet called?

solenoid

how do magnetic fields work in electromagnets

a magnetic field is produced in and around the solenoid when electric current flows in the coil, just as we get a magnetic field around a single current carrying wire.with an iron core, the strength of the magnetic field is increased while the current is flowing.
one end of a solenoid is a north pole and the other end is a south pole, just like a bar magnet

compass magnets

point towards magnetic north unless a current is applied, which then it shows evidence of a circular magnetic field