Page 49 - Physics_Form_2

Current electricity

Ammeter connection: An ammeter, which Solution
measures current, is always connected Switch
in series with the circuit component(s) to Switch
ensure that the current flowing through the
component(s) also flows through, and is Battery Battery
measured by, the ammeter.
FOR ONLINE READING ONLY
Wire Wire
Components: For beginners, connect a (a) Open circuit (b) Closed circuit
single component, e.g., a resistor, bulb, Figure 2.7
in series with a source of e.m.f. However,
depending on the requirement, if multiple Resistance to an electric current
components are used, they may be connected The flow of charge through a wire in a
in parallel and/or series configurations, and circuit can be compared to the flow of
then the system is connected in series with water through a pipe connecting two water
the source of e.m.f. reservoirs. Water flows through the pipe if
there is a pressure difference between the
Other rules two reservoirs. As it flows through a pipe,
1. Draw the circuit symbols first. it loses energy due to friction between the
2. Using a ruler, draw all the connecting moving water molecules and the pipe’s inner
wires. walls. Similarly, electric charges will flow

3. Make all the connecting wires and between two points of a conductor if one
leads straight lines with corner angles point has a higher electric potential than the
of 90 degrees as shown in figure 2.6. other; that is, there is a potential difference.
As charges flow in a material, they encounter
4. Do not cross any of the lines numerous collisions with atoms, resulting
representing conducting wires. in a resistance to the flow of charges. This
Battery is known as electrical resistance, denoted
by the letter R. In other words, electrical
Bulb resistance is the opposition to the flow of
Cell electrical current through a material.

Any material that offers low resistance to
the current flow is termed a conductor. On
the other hand, a material is said to be an
Bulb insulator if it does not allow the flow of
electric current through it. Some materials,
Figure 2.6: Simple electric circuit
known as semiconductors, have resistance
Example 2.2 between that of conductors and insulators.
The SI unit of electrical resistance is the
Draw an open and a closed electric ohm, denoted by the symbol Ω. It is worth
circuit using a bulb, battery, switch and noting that electrical current loses its energy
wire using the circuit symbols. as it flows through a conductor.

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Physics Form 2 Final.indd 43 25/10/2025 10:25