Page 68 - Physics_Form_2

Physics for Secondary Schools

4. Determine the value of the unknown resistor is equivalent to respective lengths
.
X using the formula: L and L That is,
B
A
QR ρL
X = V B
P R B = A = L B
R ρL L
5. Repeat steps 3 and 4 by using different A A A A
FOR ONLINE READING ONLY
values of P and Q to obtain several values
of X. Calculate the average value of the But
unknown resistor X. R R L R
B  X  B  X
R R L R
Questions A A
This expression can therefore be
(a) What is the value of the unknown resistor written as,
X ?
(b) What are the possible sources of errors in R  X L B  R
this activity? L A

This expression can be used
Slide wire bridge (Metre bridge) to determine the value of the
unknown resistor.
A slide wire bridge (Metre bridge) is a modified
Wheatstone bridge. It is made of one known Activity 2.8 aids on performing
resistor R, an unknown resistor R X , and a experiments regarding finding
wire of uniform cross section area, as shown unkown resistor by meter bridge.
in Figure 2.30
Activity 2.8
E K
Aim: To determine the
R R resistance of an
x
unknown resistor
using the metre
L A A L B bridge

R Materials: a resistor with
A R B
G unknown resistance,
a cell, galvanometer,
. metre bridge,

decade resistance
Figure 2.30: Metre bridge box, switch, jockey,
connecting wires
R
The ratio B is adjusted by sliding a jockey Procedure
R A
along the length of the wire. Because the wire 1. Set up the metre bridge circuit
R as shown in Figure 2.31. Let
has a uniform cross-sectional area, the ratio B the resistance box be R.
R A

62
Student’s Book Form One

Physics Form 2 Final.indd 62 25/10/2025 10:26