Electricity And Forces Flashcards
How does static electricity build up?
When charges are not free to move many of them build up, this results in a large charge when the charges finally move it causes a spark
What are the masses and charges of sub atomic particles
Proton + and 1 mass
Neutron no charge and 1 mass
Electron 1/2000 mass and negative charge
How does static build?
When two insulating materials are rubbed together electrons will be scraped off one and dumped on the other giving the one with dumped electrons a negative charge and the other positive
When electrons move from a duster to a polythene rod what charges to both take
The polythene rod becomes negative
The duster becomes positive
Common places static electricity is found
When synthetic clothes are dragged over each other like in a tumble dryer electrons are scraped off leaving static charges on both.
Car seats can rub against your clothes creating static you can get a shock when touching the metal handle.
Why does a static balloon stick
The negative balloon repeals the negative electrons on the wall leaving only positive charge which attracts therefore it sticks
Describe uses of static electricity
Spray paint gives the paint a static charge. When it sprays the negative charges push the paint away creating an even coat and the paint is also attracted to the object as it is given the opposite charge.
How do you stop static charges.
Use a conductor to ground the charge.
What is current
The rate of flow of charge
Why are metals good conductors
Because they have free electrons which can carry charge
How to calculate charge
Charge is current x time
What is voltage
It is the driving force that pushes the current round it can be though of as electrical pressure
What is resistance
Anything in the circuit which slows down the flow of charge measured in ohms
What is potential difference
It is the same as voltage
It is the energy transferred per unit of charge passed
What is 1 volt equal to
1 joule or coulomb
What happens at a junction in a parallel circuit
The current is split up depending on the resistance, but none is lost it is the conservation of energy
How to calculate potential difference or voltage
Current x resistance
What is the relationship between resistance and voltage
The resistance is proportional to the voltage at a constant temperature
What happens to a filament lamp as the temperature increases
The resistance also increases
Describe a LDR in different types of light
In bright light the resistance falls
In dark light the resistance increases
In bright light to stand out a sign needs to be as bright as possible so the resistance must be low
Describe a Temperature Dependant Resistor in different temperatures
In hot conditions the resistance drops
In cool conditions the resistance increases
Why do resistors get hot under high energy transfer
Because the electrons collide with ions in the lattice as they move through, these collisions give the ions extra energy emitted as heat. The heat increases the resistors resistance if it becomes to hot no current will flow. It can cause components to melt, this is how fuses work they melt when the current or voltage becomes to high.
What is electrical power
The rate at which an appliance transfers energy
It is calculated by potential difference x current
What is the difference between a vector and scalar
Both are measurements but a vector has a direction, for example displacement or velocity
How do you calculate time
Distance
What is acceleration and give the unit
The rate at which the velocity is changing, is is useually measured in m/s squared
What is the formula for acceleration
A x T
In a distance time graph what is the gradient
Speed
In a velocity time graph what is the gradient what do flat sections represent
Acceleration , a constant speed represented by flat sections
How to calculate distance in a velocity time graph
The area under the graph
How are forces shown
Through arrows, the larger the arrow the larger the force the direction of the arrow shows the direction of the force
What will a car with a constant speed force arrows be like
They will be exactly the same as the forces either side are balanced so it is in equilibrium
What is the force of gravity
9.81
What is the difference between weight and mass
Weight is the gravitational pull caused by gravity on your mass.
Mass is the amount of stuff you are
All objects in a vacuum do what
Fall at the same rate as there is no things to slow the items down such as air resistance and the pull of gravity is equal so they fall at the same rate
What is terminal velocity
The point of which the force pulling something down is the same as the force of air resistance and others such as drag, this causes the speed to become constant and no acceleration to occur.
What is a resultant force
The force that occurs which is in direct opposite to the force first acted I.e. Object A exerts a force on object then object ab exerts the exact opposite force on object A
What happens when the resultant force is zero
The thing will continue doing as it did I.e continue at a constant velocity
What happens if the resultant force acting on a body is not zero
They object will accelerate in the direction of the resultant force
How do you calculate force
Mass time excels ration
What type of current do cells and battery’s supply
Direct current
