Page 61 - Physics_Form_2

Current electricity

Table 2.1 Nevertheless, the reciprocal of
conductance is the resistance of the
P.d. (V) Current (A) conductor. That is,
0.2 1
0.4 G = . R
0.6 Similarly, Ohm’s law can be expressed
FOR ONLINE READING ONLY
0.8 as:
1.0 V  I it implies V  IR
1.2
where R is the constant of proportionality
Questions called resistance of a conductor. Hence,

(a) What happened to the bulb’s R = V
brightness as the p.d was increased? I

(b) Use an ICT software or otherwise to The ohm can be defined as the resistance
plot a graph of p.d against current. of a conductor such that, when a potential
difference of 1 volt is applied to two
(c) Explain the shape of the graph. What points of a conductor, a current of 1
does the nature of this graph imply? ampere flows through it. Therefore,

volt
Current flows when a cell is connected ohm = ampere
across the ends of a conductor. For a
conductor such as copper wire, the current By keeping temperature and other physical
flowing through it is directly proportional properties constant, the resistance (R)
to the potential difference across the of a conductor remains constant. This
ends of the conductor. This complies relationship enables us to determine
with Ohm’s law, which states that “The currents and voltages in electric circuits.
current passing through a conductor at
constant temperature is proportional to Activity 2.5
the potential difference between its ends.”
Aim: To determine the value of
That is, the unknown resistance by
I  V or I = kV using Ohm´s law
Materials: battery (E), ammeter (A),
where k is the constant of proportionality unknown resistance (R),
called conductance of a conductor, switch (S), voltmeter (V),
denoted by G. Hence,
rheostat (Rh) of at least

I 1 V 500  , and connecting
G = ; = wires
VG I

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Physics Form 2 Final.indd 55 25/10/2025 10:26