Electricity Flashcards
What is the rule with current and potential difference in a series circuit?
Current is the same everywhere
Potential difference is shared between components.
What is the rule with current and potential difference in a parallel circuit?
Current is shared between loops
Potential difference is the same for each loop.
What is current?
The rate of flow of charge.
What is the equation for current?
Charge / time
What is conventional current?
Current that flows from positive to negative ( sides of a battery )
What is potential difference?
The work done per unit charge between 2 points in a circuit
(or energy transferred per coulomb)
What is the equation for voltage?
Work done / charge
current x resistance
How much resistance does an ammeter have?
None
How much resistance does a voltmeter have?
Infinite
What is resistance?
A measure of how difficult it is for charge carriers to pass through a component
What is ohms law?
The law states that for an ohmic conductor, the current passing through it is directly proportional to the potential difference across it, providing that physical conditions, like temperature, remain constant.
What is an ohmic conductor?
A component that follows ohms law
What is a diode?
They are made from semiconductors and are designed to let current flow in one direction only
What are the I-V characteristics of an ohmic conductor?
Directly proportional, straight line through the origin
What are the I-V characteristics of a diode?
The forward bias is the direction in which the current is allowed to flow.
The direction of reverse bias, the resistance will be extremely high meaning only a small current can flow
Explain in terms of electron motion, why the I-V characteristics for the filament lamp is a curve.
An increase in current leads to an increase in temperature, this causes an increase in the movement of the atoms in the metal wire, causing more frequent collisions with the electrons, causing resistance to increase shown by I/V changing.
What is resistivity?
A measure of how easily a material conducts electricity, it is defined as the product of resistance and cross sectional area, divided by the length of the material
What happens to the resistivity of a thermistor if temperature increases?
The resistance will decrease, as this causes electrons to be emitted from atoms, therefore the number of charge carriers increases and so the current increases, decreasing resistance, and therefore it’s resistivity
What is Power?
The rate of energy transfer
What is the electromotive force?
The energy transferred by a cell per coulomb of charge.
What is internal resistance?
It is where electrons collide with atoms inside the battery, therefore some energy is lost before electrons even leave the battery.
What are Kirchhoff’s laws?
1) The total current entering a junction = the total current leaving it.
2) The total voltage in a series circuit (sum of all components voltage) is equal to the voltage of the battery.
What is a potential divider?
It is a circuit with several resistors connected in series across a voltage source used to produce a required fraction
