ohms law, dc circuits and kirchoffs laws Flashcards
what happens to opposite charges
attract
what happens to like charges
repel
what is resistance
Resistance opposes the flow of electric current in a circuit.
It is measured in Ohms (Ω) and is denoted by the symbol ‘R.’
equation for ohms law
V = IR
Definition of ohms law
The current and potential difference through an ohmic conductor held under constant physical conditions are directly proportional, with the constant of proportionality being resistance.
what is direct current
In a direct current, the flow of electrons is consistently in one direction around the circuit.
what is alternating current
In an alternating current, the direction of electron flow continually reverses.
how to measure current
using an ammeter, must be in series with component
what does the current through a component depend on?
The current through a component depends on both the resistance of the
Component and the potential difference across the component.
how to measure potential difference
using a voltmeter places in parallel with component
do conductors have low resistance or high resistance
low
do insulators have low resistance or high resistance?
high
what is the conductivity of an ohmic conductor
Ohmic conductors exhibit a linear relationship between the electric field (voltage) applied across them and the resulting current.
what is the conductivity of a semi conductor?
Semiconductors exhibit a non-linear relationship between voltage and current.
factors affecting semiconductors conductivity
temperature, impurities, and external conditions
what is the relationship between pd and current for a fixed resistor
For a fixed resistor, the potential difference is directly proportional to the current.
what will happen if you double the amount of energy into the resistor
Doubling the amount of energy into the resistor results in a current twice as fast running through the resistor.
example of ohmic conductor
resistor
what is a filament bulb
A filament bulb, also known as an incandescent bulb, is a type of electric light bulb that produces light by heating a wire filament until it emits visible light
what happens when an electric current passes through the filament
it heats up due to its resistance to the flow of electricity.
what happens to current in a filament bulb?
In a filament bulb, the current does not increase as fast as the potential difference.
what happens if you put more energy in a bulb
The more energy that is put into the bulb, the harder it is for the current to flow - the resistance of the bulb increases.
what happens if the p.d in a Bulb increases
As the potential difference increases, so does the temperature of the thin wire inside the bulb, the filament.
what does high temperature do in a bulb
The higher temperature increases the vibrations of the ions in the filament, which makes it harder for the electrons to get past.
what is a semi conductor diode
A semiconductor diode only allows current to flow in one direction.
what will happen if p.d tries to push current the wrong way in a diode
If the potential difference is arranged to try and push the current the wrong way (also called reverse-bias) no current will flow as the diode’s resistance remains very large.
when will Current only flow in a diode
Current will only flow if the diode is forward-biased.
relationship between resistance and p.d in a diode
The diode’s resistance is very large at low potential differences but at higher potential differences, the resistance quickly drops and current begins to flow.
inversely proportional
what is resistivity
Resistivity is a fundamental property of materials that describes how strongly a specific material opposes the flow of electric current
unit for resistivity
ohm metres
what is resistivity dependent on?
Resistivity is an fundamental property of a material and is independent of its shape and size.
equation for resistivity
P = RA/ L
P = resitivity
R - resistance
A - cross sectional area
L - length
equation to calculate power loss in cable
P = I^2 x R
what does a circuit consist of
voltage/current source
connecting wires
elements like resistors, capacitors, inductors, transistors, diodes
what is a series circuit
If all the elements of a circuit are arranged in such a way that the magnitude of current that flows through each element is equal to the total current in the circuit, then the circuit is said to be a series circuit.
properties of a series circuit
The same amount of current flows through each element.
The voltage drop across each element is not the same.
The total resistance of the circuit is the sum of the resistance of all the resistors.
If one of the elements fails, then the current will stop flowing in the whole circuit.
what are parallel circuits
If the elements of a circuit are arranged in such a way that the magnitude of the current that flows through each element is not equal to the magnitude of the total current in the circuit, then the circuit is said to be a parallel circuit.
what is voltage drop
Voltage drop refers to the reduction in voltage that occurs as electrical current flows through a conductor
(such as a wire or a circuit)
It is a natural phenomenon that happens due to the inherent electrical resistance of the conductor.
properties of a parallel circuit
The total current gets divided in different proportions in all the branches of the circuit. The proportion of current in each branch is given by the ‘current divider rule’.
The voltage drop across all the parallel elements is same.
what happens if any on element fails in a parallel circuit
If any one element fails, the current stops flowing only in that particular branch of the circuit where the faulty element exists.
what happens if an element in a series circuit stops working
: In a series circuit if ant element stops working, then it breaks the entire circuit
