Resistance Flashcards
How are the electrons in a metal arranged?
They are not associated with a particular atom
What is the term delocalised?
When the electrons in a metal are not associated to a particular atom
How is an electrical current generated?
When a circuit is provided with an energy source, the negatively charged electrons will flow towards the positive terminal of the battery
What does resistance in an electrical circuit do?
It opposes the flow of electrons
What is the measurement of resistance in an electrical circuit?
The ohm
What is the symbol for the ohm?
Ω
What does resistance in an electrical circuit cause?
The electrons to collide with the atoms sin the resistor
This causes kinetic energy to be transferred
It is transformed into thermal energy
The resistor will heat up
How can resistors be useful in appliances?
The thermal energy created by the resistor can be used to heat up a kettle
What is a variable resistor?
A resistor where the amount of resistance can be adjusted
How does a variable resistor work?
When making a circuit, the more of the resistor you allow into the circuit, the more resistance there will be
What is an example of a variable resistor?
A graphite pencil
When the crocodile clips are closely connected, there is little resistance
The further apart the crocodile clips are the more the resistance there is
What does incandescent mean?
When an object emits light as a result of being heated
What is a rheostat?
It is a common variable resistor
Why are rheostats used in circuits?
They are used to adjust the current
Where would a rheostat be useful?
Sound equipment (adjust volume) Dimmer switches (adjust light) Control the speed of motors
What does LED stand for?
Light Emitting Diode
What is a diode?
A diode is an electrical component that has a very low resistance to current flow in one direction, and high resistance in the other direction. Therefore, current can only move in one direction.
What does a Sankey diagram show?
How the input energy is transformed
What is the relationship between resistance and current?
Inverse.
As the resistance increases, the current decreases.
⬆️R ⬇️I
What are the two functions of a resistor?
To create an energy transformation
To control the current within a circuit
How do you write the equation for a lightbulb?
Electrical ➡️ light + thermal
Why do the arrows in Sankey diagrams need to be a specific width?
No energy can be lost or gained
What is an alloy?
A mixture of metals
Which alloy is usually used as heat elements?
Nichrome
Which elements form nichrome?
Nickel
Chromium
What are the resistance levels of alloys?
They are good resistors
What is resistance?
The opposition to electric current in a circuit
What is a resistor?
An electrical component used to add resistance to an electrical circuit
What are the factors that affect resistance?
The type of material
Length of the resistor
The thickness of the resistor
The temperature of the resistor
What length of resistor offers more resistance?
The longer the resistor, the more resistance it provides
What width of resistor offers more resistance?
Thinner resistors offer more resistance
What temperature of a resistor offers more resistance?
Hotter resistors resist more
What is an electrical current?
The rate of charge flow in a closed, electrical circuit
What is an electric charge?
Physical property of matter that causes it to experience a force when close to other electrically charged matter
What happens to the current when a resistor is added to the circuit?
It will slow down
They have an inverse relationship. Increase resistor, decrease current
What is input energy?
The energy put into the system
What is the output energy?
The energy that comes out of a system
How can energy be wasted?
It is released into the surroundings, rather than being transformed into useful energy
How can you increase the resistance in a kettle?
Coil it to increase the surface area
What is a filament?
The small, coiled resistor in an incandescent light bulb
What is a filament usually made out of?
Tungsten
How does an incandescent lightbulb work?
Electrical input energy is transferred to the filament.
The electrons bump into the atoms of the filament, transferring kinetic energy to them.
This kinetic energy is transformed into radiant and thermal energy.
Why does the element in a toaster glow?
The friction between the electrons and the resistor is transformed into radiant and thermal energy
How does a rheostat change the amount of resistance in a circuit?
The more resistor the electrons have to flow through, the slower the current becomes
Why do you need an additional resistor when instituting LED light bulbs?
They are very sensitive to high currents
In a Sankey diagram, which arrow will show the useful energy?
The one going straight
What is the formula for resistance?
R= V/ I
What is the symbol for current?
I
Intensity of current
What is the relationship between current and resistance?
Inversely proportional
Resistance increases current decreases
What is gauge?
The thickness of a resistor
Why does a hot wire increase resistance?
They vibrate faster, which makes it harder for the electrons to flow
How does a thin wire increase resistance?
Fewer electrons can flow through at any given time
How does a long wire increase resistance?
The electrons have to travel further to get through it
Why is copper used for wiring?
It is cheap
It conducts coulombs well
It doesn’t heat up quickly
