Question 1 Report
A wire P has half the diameter and half the length of a wire Q of similar material. The ratio of the resistance of P to that of Q is
Answer Details
Resistance α α lengtharea l e n g t h a r e a
RQRP R Q R P = LQAPLPAQ L Q A P L P A Q
LQ = 2LP
DQ = 2DP
AP = π π (2DP)22 ( 2 D P ) 2 2
= π π DP
AQ = π π (DP)22 ( D P ) 2 2
= 14 1 4 π π DP
therefore, RQRP R Q R P = 2LP×πDPLP×14πDP 2 L P × π D P L P × 1 4 π D P
= 2 : 1