Video Transcript
The diagram shows an electric
circuit containing a cell and a bulb. Complete the following
sentence. The blank create, or creates, a
potential difference across the blank. (A) Bulb, cell; (B) bulb, wires;
(C) wires, bulb; (D) cell, bulb.
First, let’s review some basic
components in electric circuits and their functions. In electrical circuits, the wires
are represented by straight lines and connect all the components in the circuit. Wires are conductors that easily
allow electric charges to travel through the circuit. A bulb, represented by a circle
with a cross inside it, will emit light when electric charges flow through the
bulb. A cell in an electric circuit does
work on electric charges in the circuit while they move from the positive terminal
of the cell to the negative terminal of the cell. When there is an electric potential
difference across a component, this means that electric charges either gain or lose
energy when they pass through the component. A component that creates a
potential difference must increase the energy of electric charges that move through
it.
Taking this into consideration,
let’s determine which of the components shown is the component that creates an
electric potential difference. The only one of these components
capable of transferring energy to electric charges to increase their energy is the
cell. We see then that the cell creates
an electric potential difference. Option (D) is the only option that
fills the first blank with the word “cell.” So, the other options must be
incorrect. We should, however, check that
option (D) is fully correct.
Option (D) states that the second
blank is filled by the word “bulb.” This means that the bulb is a
component of the circuit that has an electric potential difference created across it
by the cell. When electric charges pass through
the bulb, these electric charges decrease in energy. The energy lost by the electric
charges is released as light. We see then that the correct answer
is option (D). The cell creates a potential
difference across the bulb.
