Video Transcript
The following diagrams each show
two cells connected in series. In which of the diagrams are both
cells aligned the same way?
In this question, we are asked to
determine which of two diagrams shows both cells aligned in the same way.
To work out what it means for two
cells to be aligned the same way, let’s first recall the function of a cell in a
circuit. A cell has a positive terminal,
that’s represented by this longer line, and a negative terminal, represented by this
shorter line. A cell provides a potential
difference across a circuit, causing charges to flow around the circuit from one
terminal of the cell to the other.
This flow of charges is an electric
current. The direction of conventional
current is from the positive terminal to the negative terminal. So, we can think of a cell as
pushing positive charges around the circuit in this direction from the positive to
the negative terminal. In order for cells to be aligned
the same way then, they should both be acting to push charges in the same
direction.
Consider what would happen if the
two cells were connected like this, with the positive terminal of the left-hand cell
connected to the positive terminal of the right-hand cell. If we placed these two cells into a
circuit like this, then the left-hand cell would be trying to push the charges this
way around the circuit, from its positive terminal to its negative terminal, while
the right-hand cell would by trying to push them this way, the opposite
direction. So, these two cells are not aligned
the same way. We therefore know that the diagram
in option (B) is not our answer.
However, if the two cells are
connected like this, with the positive terminal of the left-hand cell connected to
the negative terminal of the right-hand cell, then both cells are acting to push the
charges in the same direction, clockwise, around the circuit. So, in this case, the two cells are
aligned the same way. The correct answer is therefore
option (A).
