EMF and internal resistance

In summary, the person is requesting help with a homework problem involving a cell supplying current through resistors connected in parallel and series. They are looking for guidance on how to calculate the EMF and internal resistance of the cell in both scenarios. The expert advises using two equations with two unknown variables to solve the problem.
  • #1
AdrianP123
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Homework Statement


Hi, my first post here. :smile:
Anyway I am struggling with this homework, can someone help me out, show me what to do please.

1)a cell can supply a current of 1.2A through two 2ohm resistors connected in parallel. When they are connected in series the value of the current is 0.4A. calculate the EMF and the internal resistance of the cell.

2) A cell is joined in series with a resistance of 2ohms and a current of 0.25A flows through it. When a second resistance of 2ohms is connected in parallel with the first the current through the cell increases to 0.3A. What is the EMF, and what is the internal resistance of the cell?

I really have no idea what to do, but i need to do this very quickly.

Any help would be greatly appreciated
 
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  • #2
a cell can supply a current of 1.2A through two 2ohm resistors connected in parallel.

EMF = 1.2 ( 1 Ohm + Ri )

When they are connected in series the value of the current is 0.4A

You write the equation.

Two equations and two unknown variables ( Ri and EMF ). Solve !
 

Related to EMF and internal resistance

1. What is EMF?

EMF stands for electromotive force, which is the energy that drives electrons through a circuit. It is measured in volts and represents the potential difference between two points in a circuit.

2. What is internal resistance?

Internal resistance is the resistance within a battery or power source that limits the amount of current that can flow through it. It is caused by the resistance of the materials used in the battery and can reduce the overall voltage output of the battery.

3. How does EMF and internal resistance affect circuit performance?

EMF and internal resistance can both impact the performance of a circuit. EMF can determine the overall voltage output of the circuit, while internal resistance can limit the current flow and reduce the voltage output. This can result in a decrease in the efficiency and effectiveness of the circuit.

4. How can EMF and internal resistance be measured?

EMF can be measured using a voltmeter, while internal resistance can be calculated by measuring the voltage output of a circuit with and without a load and using Ohm's law (V=IR) to calculate the internal resistance.

5. What factors can affect the levels of EMF and internal resistance in a circuit?

The levels of EMF and internal resistance in a circuit can be affected by various factors such as the type and quality of the battery or power source, the temperature, and the age and condition of the circuit components. Additionally, the type of material used in the circuit can also impact the levels of EMF and internal resistance.

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