P3 - Current and electricity Flashcards
Draw the circuit symbols for cell battery switch power supply variable resistor thermistor diode led ldr
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what is current?
The rate of flow of charge
what way does conventional current flow
conventional current flows from positive to negative, the opposite way to electron flow
What is potential difference/ voltage?
the work done in a moving unit charge between the two points
What’s the definition of resistance?
What does resistance effect?
if you put a potential difference across an electrical component, a current will flow. How much current you get for a particular potential difference will depend on the resistance of the circuit
resistance effects the potential difference as a higher resistance means a higher potential difference is needed to provide more energy to the current so it flows through. Which therefore effects current
What’s the definition of a ohmic conductor?
Ohms law states that provided the physical conditions such as temperature, remain constant, the current through an ohmic conductor is directly proportional to the potential difference across it
What surroundings affect resistance?
light level, temperature
What’s the shape of a iv graph for a ohmic conductor?
what’s the shape of a iv graph for a filament lamp?
Y = X graph
as p.d increases the gradient of current decreases, same w negative
Why a iv graph of a filament lamp get shallower?
When current flows through a metal conductor, (the filament in the filament lamp), some of the electrical energy is transferred into heat energy and causes the metal to heat up. This extra heat energy causes the particles in the metal to vibrate more. These vibrations cause an increase in collisions so the electrons cant flow as easily
What is the function of a diode?
what is the characteristic of the diode in reverse?
A diode only lets current flow in one direction.
Very high voltage so there is a tiny current
what is the shape of a iv graph for a diode?
very sudden steep gradient on the positive side, in reverse very shallow line as very little current can flow
what is the definition of resistivity?
resistivity is the resistance of a 1m length wire with a 1 metre squared cross sectional area
What is the difference between resistance and resistivity?
Resistance Is a property of an object and it depends on the material and dimensions of the object. Resistivity is the property of a material
What does A,L,R,P stand for in the resistivity equation?
p = resistivity A = cross sectional area L = length R = resistance
what is a semiconductor?
what happens when temperature increases?
semiconductors are a group of materials that aren’t as good at conducting electricity as metals as they have far fewer available charge carriers.
When there is an increase in temperature more charge carriers can be released and the resistivity of the material decreases
