V=IV,IV graphs

• current is the rate of flow of charge
• potential difference is the difference of electrical potential between two points
• resistance is the measure of how easy it is for current to flow
• the unit of current is amps (A)
• the unit of potential difference is volts (V)
• the unit of resistance is ohms (Ω)
• the formula for current is I=V/R (current=potential difference/resistance)
• the formula for potential difference is V=IR (potential difference=current x resistance)
• the formula for resistance is R = V/I (resistance= potential difference/current)
• According to Ohm's Law, the potential difference (V) across a conductor is directly proportional to the current (I) flowing through it and inversely proportional to the resistance (R) of the conductor.
• the IV graph for a resistor is directly proportional because potential difference and current increase at the same time
• the IV graph for a light bulb curves like an s through the origin this is because as p.d. increases the temp of the filament increases, this causes the ions to vibrate which means electrons in the current collide with ions more. resistance increases so the current and p.d. are no longer directly proportional.
• the IV graph for an light emitting diode (LED) is flat on the negative side and slopes upwards on the positive side because a diode has very high resistance so the current can only flow in ONE DIRECTION
• the graph for a thermistor curves downwards , as the resistance decreases the temperature increases because thermistors are made of semi conducting material.
• the graph for light dependant thermistors (LDRs) curve downwards , as resistance decreases the temperature increases, this is the same as thermistors
• the equation for voltage is voltage= energy/charge
• A potential difference of one Volt is equal to one Joule of energy being used by one Coulomb of charge when it flows between two points in a circuit.
• the equation for charge is Q=IT Q=charge I=current T=time
• what is current caused by?

  a source of potential difference
• what is an ohmic conductor?

  A conductor that obeys Ohm's law.