We have come across circuit diagrams that has the batteries, resistors and so on. We do mention the direction of flow of current in the circuit with the help of arrow marks. We have also come across Kirchhoff’s first law that states that current flowing into a node (or a junction) must be equal to current flowing out of it. Some of us have may have raised a question of what happens to the current that flows across a resistor. Consider a water tap and a gardening hose water pipe. If the breadth of the pipe is larger, the water flows out easily from a large diameter. If the breadth of the pipe is smaller than the normal size, then the water does flow out but from a small diameter. The point is, the velocity at which the water flows at both the ends of the pipe is the same. Though the velocities are different for different diameters of pipe,the amount of water that enters the pipe, leaves the pipe. If there is a difference in the velocities at then ends, it means that there is either a leak in the pipe or a region in the pipe where the water is stored which leads to bursting of the time after a while. The amount of water is analogous to the amount of charge(current) and the pipe is analogous to the resistor (larger diameter pipe- less resistance; smaller diameter pipe- more resistance). The amount of charge entering the resistor is same as the charge flowing out of the resistor and therefore there is no reduction in the value of current.
