electrical charge and currents

Name one thing needed for electrical charge to flow through a circuit

Potential difference

Equation for charge flow, time and current

Charge flow = current x time

Describe current in a single loop circuit

The same at any given point

What does current through a component depend on

Resistance of the component and the potential difference across it

Greater resistance =

Smaller current for a given potential difference across a component

Current, potential difference and resistance equation

Potential difference = current x resistance

Outline resistance of a wire practical

*

Variables in resistance of a wire practical

Dependant = resistance

Independent = length of wire

Control = material of wire, temperature and cross sectional area of wire

Resistor / ohmic conductor graph

Filament lamp graph

Diode graph

Explain a diode graph

The current can only flow in one direction as the resistance the other way is very high so remains at 0 current until it sharply increases at a voltage of around 0.7. This threshold means the resistance drops significantly and current begins to flow

Explain an ohmic conductor graph

The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes.

Explain a filament lamp graph

Curved because the resistance is not constant and increases alongside temperature. As temperature rises, atoms in metal filament vibrate so free electrons struggle to get through, increasing resistance again and flattening the graph.

The resistance of a thermistor _______ as the temperature increases.

Decreases

The resistance of an LDR decreases as light intensity _______

Increases

Explain the required practical for the iv graphs

What are the variables in the iv graph practical

Potential errors in length of wire practical

Zero error

Ruler not clipped at 0 as wore thick or inaccurate

Switch is overused and temperature increases