Contents
What is the internal resistance of the power supply?
All power supplies have some resistance between their terminals called internal resistance. This causes charges in the circuit to dissipate some electrical energy in the power supply itself. The power supply becomes warm when delivering a current.
Does power depend on internal resistance?
The smaller the internal resistance for a given emf, the more current and the more power the source can supply.
What is the resistance of a power source?
In a closed circuit a current I will be drawn from the power supply and the voltage at the terminals, called the terminal voltage V will typically fall below V∝: V = V∝ – RI (1) R is called the output resistance of the power source. resistance of the current meter (ammeter) is zero).
Why is internal resistance of an electrical source important?
The internal resistance of a source of electrical energy is an important factor when considering how to get the source to deliver maximum power to an electrical appliance (the load) connected to it.
How are load resistance and internal resistance related?
The equivalent resistance of the circuit is (since the load resistance is in series with the internal resistance), so the current flowing in the circuit is given by Thus, some of the power output of the battery is immediately lost as heat dissipated by the internal resistance of the battery.
How is the resistance of a power supply determined?
When the power supply is not connected to a circuit, there will be no current flowing, therefore: V = E – 0 x r . V = E . i.e. the e.m.f voltage, is equal to the open circuit terminal voltage of the power supply. The internal resistance can be determined, by connecting a circuit of known resistance and measuring the current that flows.
How to find the internal resistance of a battery?
If the emf ( ℰ) of a battery is known, its internal resistance ( RINTERNAL ) can be found by measuring the current ( I LOAD ) that flows across a load resistance ( RLOAD ) with a known value. Since the internal and load resistances are in series, we can use Kirchhoff’s voltage law and Ohm’s law to obtain the following formula: