# Physics

posted by .

The internal resistance of a dry cell increases gradually with age, even though the cell is not used. The emf, however, remains fairly constant at 1.5 V. Dry cells must be tested for age at the time of purchase by connecting an ammeter directly across the terminals of the cell and reading the current. The resistance of ammeter is so small that the cell is practically short-circuited. (a) The short-circuit current of a fresh No. 6 dry cell (1.5 V, emf) is 25 A. What is the internal resistance? (b) What is the internal resistance if the short circuit current is only 10 A? (c) The short circuit current of a 6 V storage battery may be as great as 1000 A. What is its internal resistance?

ok..I am confused are we suppose to use the V=E-Ir? I don't know what equation to use!

• Physics -

Ohm's law can be stated as:
(resistance in ohms)= (voltage in volts)/(current in amps) .

For part (a):
resistance=(1.5V)/(25A)=0.06 ohms

Use the same equation for (b) and (c).

## Similar Questions

1. ### Science

Every cell in the body has a full complement of all genes, however each cell type reads only certain genes. For example, both white blood cells and liver cells have genes for making digestive enzymes but they do not read them. how …
2. ### chemistry

Nitrogen gas, N2, is usually a very inert gas and thus, is often employed in dry boxes. However, it would be a poor choice for use in a dry cell with which of the following substances?
3. ### biology

Organisms must be able to adapt to a changing external and internal environment. An organism's ability to maintain a stable internal environment is known as homeostasis. How does a cell's membrane help an organism maintain homeostasis?
4. ### Physics

A capacitor of capacity C is charged fully by a cell of emf V/2 and then it is disconnected and again connected with a cell of emf V (+ve plate of capacitor with +ve terminal of cell and vice versa). The heat developed in connecting …
5. ### science

which of the following is not part of cell theory?
6. ### Chemistry

In a dry cell, MnO2 occurs in a semisolid electrolyte paste and is reduced at the cathode. The MnO2 used in dry cells can itself be produced by an electrochemical process of which one half-reaction is shown below. Mn2+(aq) + 2 H2O(l) …
7. ### chemistry

In a dry cell, MnO2 occurs in a semisolid electrolyte paste and is reduced at the cathode. The MnO2 used in dry cells can itself be produced by an electrochemical process of which one half-reaction is shown below. Mn2+(aq) + 2 H2O(l) …
8. ### physics

a cell of emf 10v and internal resistance 2ohms is connected in series with an ammeter resistance 0.5ohms and a load of resistance 7ohms. Calculate (A) the potential difference across its terminal (B)the voltage drop
9. ### math

Find the minimum number of cells connected in two rows in parallel required to pass a current of 6 A through an external resistance of 0.70 ohms. Take the emf of each cell as 2.1 volts and internal resistance of each cell as 0.5 ohm..
10. ### Physics

A cell of emf 2v and internal resistance of 1ohms passes a current through an external load of 9ohms.calculate the potential difference across the cell

More Similar Questions