Physics - Electricity

What is internal resistance?

The loss of potential difference in the battery

What is the equation for total emf across the circuit?

Potential difference in circuit + volts lost (internal resistance)

What is the terminal pd?

The voltage that is supplied to the circuit.

What is the load resistance?

The resistance of the circuit from the terminal pd.

What direction does charge flow in?

Positive to negative terminal

What direction do electrons flow in?

Negative to positive terminal

What is Ohm’s Law?

Potential difference is proportional to current as long as temperature and resistance is kept constant

For a graph of I against V, why does the line curve for a filament lamp?

Resistance is no longer constant. The delocalised electrons collide with the ionic lattice which causes them to vibrate more and increase the temperature. This causes a larger current and increased resistance.

What is significant of the x intercept of a I V graph for a diode?

No current flows until a pd of (the x intercept) is placed across the diode.

What is a superconductor?

Materials that have zero resistance at or below the critical temperature.

What is resistivity?

The resistance of a 1m length of wire with a 1m² cross sectional area. Measured in Ohm Metres

Rules in a series circuit

Total V is chared between components, current is the same at all points in the circuit, the total resistance is the sum of all the resistances.

What is kirchoffs second law?

Sum of the EMFs is equal to the sum of the drops in a closed loop.

If two resistors are non-identical what heppns to the share of the total V?

The one with the greater resistance will take a greater share of the V as current is constant.

Rules for parallel circuits

The pd across each branch is the same as the pd of the cell, current is split between branches, more resistors in parallel reduced total resistance

What is kirchhoffs 1st law?

Charge is conserved at any junciton in a circuit.

What are the properties of a NTC thermistor?

If the temperature increases, resistance would decrease

What are the properties of a LDR?

Increasing light intensity decreases resistance

What is Power?

Rate of energy transfer

What is DC?

A potential difference that acts in one direction, resulting in a direct current

What is AC?

Alternating PD results in an alternating current that reverses direction at a frequency of 50Hz and 230V

What is the EMF of a circuit?

The energy transferred by a cell per coulomb of charge