vk6kro said:Maybe you should give an example.
Resistors are not the same as voltage sources, but there are similarities.
If a resistor has a large current passing through it, and you place a much larger resistor across the first one, it will have almost no effect on the voltage across the first resistor and will draw a current as if it had been placed across a voltage source.
vk6kro said:You really need to accept the initial conditions for this to work.
Suppose you had a radio that normally ran off 6 volts from 4 "C" cells.
All you had was a 12 volt battery from a car and two 12 volt rear lamps, also from a car.
The lamps draw 3 amps if placed in series across the 12 V battery. So they have a resistance of 4 ohms total or 2 ohms each.
Across each of them is 6 volts. Now if you connect the radio across one of the lamps, it may draw 50 mA or 10 mA depending on how loud the sound was.
If it drew 50 mA at 6 volts, it has a resistance of 6 V / 0.05 A = 120 ohms.
If you put this across one of the lamps, the resistance of the pair would be 1.97 ohms.
This would cause the voltage to drop from 6 volts to 5.95 volts.
So, the car lamp is behaving just like a source of EMF and giving a very stable voltage.
It is very inefficient to do this, but it gives a result.
amaresh92 said:please could you tell me that ,In dc equivalent circuit the resistors are replaced by cell.why is it so?though the resistor gives voltage drop where cell provides a emf then how does these are equivalent?
thanks.
sophiecentaur said:They are not really equivalent at all - despite the fact that you can measure a potential difference across them both. A cell is a source of power and a resistor is a dissipator of power. All you can say is that, in any circuit, under a specific set of conditions, the values of voltage and current in that circuit will be the same IF you replace the resistor by a cell with the same voltage. It can even apply for AC, if your 'voltage source' has the right signal on it.
What I'm saying is that the concept of 'equivalent circuit components' is for analysis and not really intended to be applied practically. I remember, when I was very young, looking at a complicated equivalent circuit for a transistor, with all sorts of current and voltage sources in it, and being laughed at (much derision from fellow students, of course), when I suggested you could "build" a transistor that way.
A DC equivalent circuit is a simplified representation of a complex circuit that behaves in the same way in terms of voltage and current as the original circuit. It is used to analyze and understand the behavior of a circuit without having to consider all of its individual components.
A resistor is a passive component that resists the flow of current in a circuit, while a cell is an active component that provides a source of electrical energy. In a DC equivalent circuit, a resistor is represented by a single resistance value, while a cell is represented by a voltage source.
In a DC equivalent circuit, resistors and cells are connected in series or in parallel. In series, the components are connected end-to-end, while in parallel, the components are connected at their terminals, allowing current to flow through multiple paths.
In a series circuit, the equivalent resistance increases when resistors are added and decreases when resistors are removed. In a parallel circuit, the equivalent resistance decreases when resistors are added and increases when resistors are removed. The addition or removal of cells does not affect the equivalent resistance in either type of circuit.
The purpose of using a DC equivalent circuit is to simplify the analysis of a complex circuit and to better understand its behavior. It allows for easier calculation of voltage, current, and power, and can also help identify potential issues or improvements in the circuit design.