P3 - Electric Circuits Flashcards
Objects with like charges…
Repel each other
Objects with opposite charges…
Attract to one another
Electric current is…
The flow of charge
Electric current is measured in…
Amperes
In an electric circuit the metal conductors contain…
Many charges that are free to move
In metallic conductors an electric current is…
The movement of free elections that are present throughout such materials
In a metal conductor there are ______ free electrons free to move but in an insulator there are ______ free electrons free to move
Many, few
An ammeter should be connected in a ______ circuit
Series
When a circuit is made the battery causes these free charges to move but…
They are not used up and instead flow in a continuous loop
The larger the voltage in a given circuit…
The greater the current
Components…
Resist the flow of charge through them
The larger the resistance in a given circuit…
The smaller the current will be
Resistance of connecting wires is…
So small it can usually be ignored
When electric charge flows through a component, work is done by _________ and energy is transferred from it to the component
The power supply
Power is…
a measure of the rate at which electrical power supply transfers energy to an appliance or decide and/or its surroundings
Resistors get hotter when there is an electric current flowing through them which is caused by…
Collisions between the moving charges and ions in the wire
This heating effect makes a lamp filament hot enough to glow
LDR’s resistance ________ as the light intensity _________
Decreases, increases
Thermistors’ resistance ________ as temperature __________
Deceases, increases
Two+ resistors in a series have more resistance than one on its own because…
The battery has to move charges through both of them
Two+ resistors in a parallel circuit provide less total resistance than one on its own because…
They provide more paths for the charges to move along
Ohms law…
Resistance=voltage/current
Voltmeters should be attached in a _______ circuit
Parallel, to show the p.d between any two chosen points
Voltage across a battery provides…
A measure of the ‘push’ of the battery on the charges in the circuit
Ignoring resistance, if you increase the voltage across a component…
Current through the component will increase
When two objects rub together…
They become charged because electrons are transferred from one to the other
Added batteries in a series circuit mean…
- The total p.d is the sum of their individual p.ds. Average cell has 1.5V so if cells are connected in the same direction a p.d of 3.0V but if in different directions 0V
- more cells means more p.d produced across each component which means more current through each component as a result
More batteries added in a parallel circuit…
- Voltage remains the same
- more current capacity because each battery has its own path to the circuit without the restriction presented by the internal resistance of the other battery. This does not necessarily mean current increases.
When two or more components are a connected in a series to a battery…
- the current throughout each component is the same
- the p.d across each component is equal to the p.d of the battery
- the p.d is largest across the component with the greatest resistance
- the change in the resistance of one component will result in the change in the p.d across all components
The p.d of each component in a series equal the p.d of the battery because…
The work done on each unit of charge by the battery must equal the work done by it on the circuit components
The p.d is largest across the component with the greatest resistance in a series because…
More work is done by the charge moving through a large resistance than a small one
When several components are connected in a parallel circuit the their potential differences are _______ to that of the battery
Equal
When several components are connected in a parallel circuit the current through each component is ________
The same, as if it was the only component present
When several components are connected in a parallel circuit the current is _______ across the component with the smallest resistance
Largest
When several components are connected in a parallel circuit the current is largest across the component with the smallest resistance because…
The same battery voltage causes a larger current to flow bough a smaller resistance than a bigger one
Generators produce mains electricity by…
A process called electromagnetic induction
When a magnet is moving into a coil of wire…
- A voltage is induced across the ends of the coil.
- if a magnet is moving out of the coil or the other pole of the magnet is moving in then the voltage is induced in the opposite direction
- When the ends of the coil are attached to a circuit a current will flow
A changing magnetic field caused by changes in the current of one wire can…
Induce a voltage in a neighbouring coil
A changing current in one coil of a transformer will cause…
A changing magnetic field in the iron core which in turn will induce an changing potential difference across the other transformer coil
A transformer can…
Change the size of an alternating voltage
The size of a voltage induced by a magnet rotating in a coil of wire can be increased by…
- increasing the speed of the rotation of the magnet
- increasing the strength of its magnetic field
- increasing the no. of turns on the coil
- placing an iron core inside the coil
The induced voltage across the coil of an a.c generator…
Changes during each revolution of the magnet
When the current is always in the same direction…
It is a direct current, such as in a battery
____ is used as it is easier generate than _____ and is easier to distribute over long distances
A.c, d.c
The mains supply is…
A.c and 230V
A current carrying wire or coil can exert a force on…
A permanent magnet or on another current-carrying wire or coil nearby
If a current-carrying wire is placed in a magnetic field whose lines are at right angles to the wire…
The current-carrying wire experiences a force at right angles to both the current direction and the lines of force of the field
If a current-carrying wire is parallel to the lines of force of a magnetic field…
It experiences no force
A motor effect can be used to…
Produce continuous rotation of the coil by using a commutator to ensure that the direction of the current in the coil is reversed at an appropriate point in each revolution
Motors can be used in domestic devices such as…
DVD players and electric motor vehicles
