Question

Construct a circuit containing two 10-? resistors in series, as shown below.

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Place the crosshairs of the noncontact ammeter just before each resistor to measure the current through the top and bottom resistors. How do these currents compare?

Answer 1

Concepts and reason

The concept required to solve this problem is of the series circuit and ammeter.

Initially, discuss about the idea and the non-ideal case of an ammeter. Then apply this concept for placing the crosshair of a noncontact ammeter to find the current through the top and bottom resistance.

Fundamentals

When the two resistances are connected in series, the current through them will same and the applied voltage will be the sum of voltages through each component.

Ammeter is a device used to measure the current in the circuit. If the resistance is present in the circuit, the value of the current will decrease. So, the resistance of an ammeter must be as low as possible. For an ideal ammeter, internal resistance is taken as zero.

But, all the devices have their own resistance. It can be minimum but zero is not possible. So, in all types of devices, there will be a voltage drop.

The circuit containing two resistors having the resistance 10 ohms and the battery of voltage 9.00 volts is shown below:

Figure: Circuit diagram

Here, A, A’, B and B’ are the points near the resistances where the crosshair can be placed.

Here, the crosshair of the ammeter is placed at points A and A’. Here, as it is not given that the ammeter has internal resistance, we will consider the internal resistance of the ammeter we are using is zero.

Then the cross-hair of the ammeter is placed at the points B and B’. Here also, the internal resistance of the ideal ammeter is zero. So, there will be no potential drop at each resistor. It shows that the current flowing through both the resistors is same.

Ans:

The currents in top and the bottom resistance is same.