The current in a single-loop circuit with one resistance R is 5.0 A. When an additional resistance of 2.0 is inserted in series with R, the current drops to 4.0 A. What is R?
The value of R is.
Write for emf of the battery when the circuit has only resistance R and when R’ is inserted in the circuit using Ohm’s law. Equating them will give the value of R.
Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
Formulae are as follow:
Where, I is current, V is voltage, R is resistance.
Let the battery be emf V. Then, Ohm’s law gives,
When R’ is inserted in the circuit in series with R, the total resistance of the circuit becomes R+R’.
Then emf is given by,
Equating the equations 1) and 2) gives,
Hence, the value of R is .
Therefore, using Ohm’s law, the unknown resistance in the circuit can be found.
Each of the six real batteries in Fig. 27-68 has an emf of and a resistance of. (a) What is the current through the (external) resistance? (b) What is the potential difference across each battery? (c) What is the power of each battery? (d) At what rate does each battery transfer energy to internal thermal energy?
What is the equivalent resistance of three resistors, each of resistance R, if they are connected to an ideal battery (a) in series with one another and (b) in parallel with one another? (c) Is the potential difference across the series arrangement greater than, less than, or equal to that across the parallel arrangement?
A simple ohmmeter is made by connecting a flashlight battery in series with a resistance and an ammeter that reads from 0 to , as shown in Fig. 27-59. Resistance is adjusted so that when the clip leads are shorted together, the meter deflects to its full-scale value of . What external resistance across the leads results in a deflection of (a) , (b) , and (c) of full scale? (d) If the ammeter has a resistance of and the internal resistance of the battery is negligible, what is the value of ?
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