ELECTRICITY Flashcards
What will happen if the 2 ends of the cell aren’t connected on the outside
The reaction inside the cell, will occur only to a small extent and then stop
What is the difference between the 2 ends of the battery reflected by
The potential difference of the cell measured in volts
If the ends of the cell are connected by a closed circuit what can happen
The Chemical reaction can draw in electrons from the conductor at the positive side and electrons can flow out of the cell into the conductor at the negative side
How do the stream of electrons flow
From negative to positive
What causes a flat battery
When all of the chemicals in the cell are used up
What is a closed circuit
Uninterrupted pathway for current to flow from the positive end to the negative
What is an open circuit
Normal path of current has been interrupted by the disconnection of one part of its conducting pathway from another
What is an electrical cell
A system in which certain chemical reactions can cause the flow of electricity through an external circuit
What is a battery
A group of cells connected together
What is the total voltage of for cells in series
The sum of all the voltages of individual cells
What is the total voltage for cells connected in paralllel
The same as for one cell
What is a short circuit
When The 2 ends of a cell battery are connected by a simple conducting wire
Why do electrons flow easily through a short circuit
Electrons flow easily as it has very little resistance. A very big electrical current will flow very rapidly from the negative to the positive side of the cell.
What is a resistor
A conducting material selected to control the current in a closed circuit and to provide useful energy transfer in a circuit
What causes resistance
A measure of how difficult it is for electrons to move from one point on a wire to a second point
When electrons move in a wire they don’t move in straight lines, they collide with the atoms in the wire.
What is a basic resistor
Provides resistance but performs no other function. Only to control the current
What is a rheostat
Basic resistors whose resistance can be adjusted by the slider
What are heater resistors
The resistance of a heater converts electrical energy to heat and light energy
How are light bulbs and LED lights resistors
Electrical energy is converted into light and heat energy
How are Motors resistors
Converted electrical energy to mechanical / heat / sound energy
What are the factors affecting resistance and explain them
Type of material - different conducting materials have different resistance to electrical current.
Thickness of conductor - the thinner the conductor the more resistance it has
Length of conductor - the longer the conductor, the more restistance it provides.
The temp of the conductor - the hotter the more resistance
Unit of resistance
What is a series circuit
A closed circuit, in whitch the current follows one path only
The more resistors the higher the resistance
Total restistance calculated by adding all of the restistance together
What is a parallel circuit
Circuit divided into 2 or more paths. Each resistor provides an alternate route for current to pass around circuit. Current splits between resistors. More resistors in parallel the lower the resistance. Easier for current to pass through 2 pathways instead of one
What is the equivalent resistance of resistors always lower than in paralalel
Always lower than the smallest resistance in parallel pair
What is electric charge measured in and what is this
Coulombs. One coklumb of charge is equal to 6,25 x 10 [18] electrons
What is current
Rate of flow of electrical charge
What is current measured in and what is this
Amos, and this is the current flowing when one coulomb of charge passes a point in the circuit every one second
What is current measured with
An ammeter placed in series in a circuit
Desribe the current in a series circuit
Current isThe same at every point of the series circuit ( hosepipe) electrons at one point can’t move faster than those at another point
What happens with current in parallel
The current divides between the resistors but the sum of the two currents is equal to the total (un split ) current in the circuit
How do currents glow brighter
When they have more current flowing though them. More restistance = dimmer light ( lower current)
What is conventional current
Flow of electrons is from Positive to negative
What happens as current passes through resistors
The energy of the current is converted into other forms of energy . Current loses energy
What is potential difference
Between 2 points in a circuit is the work done or energy released to move on collumb of charge between those 2 points in a circuit
How is potential difference measured
Using a voltmeters
How does a voltmeters work
Connected parallel to part of the circuit measured, clips are connected to the 2 points between where the voltage is measured,
What is the voltage drop
The total volts the current loses
Where are volts usually lost
In the resistors
What causes a higher potential difference across resistors
High restistance
What happens with potential difference in parallel
The current splits into 3 parts. Each part can only follow one of the 3 paths
What is an amp
One amp is the current flowing when one coulomb of charge passes a point in the circuit every one second
What is resistance
The opposition that a substance offers to the flow of electric current
What are the 3 ways restistance is measured
Ammeter in series. Voltmeter in parallel over the resistor or by using the formula R = v / I
What is an ohm
A restistance between 2 points of a conductor when a constant potential difference of 1.0 volt, applied to these points , produces in the conductor a current of 1.0 ampere.
How does a coulomb loose energy and why
As it moves through a resistor, each coulombs energy is converted into heat, light or mechanical energy
What is the potential difference across the resistor
The number of joules of electrical potential energy lost by each coulomb of charge as it passes through the resistor
How do electrical cellls work
A chemical reaction happens Which results in one cell having extra electrons and the other having too few electrons (becoming positive)
