Answer: (a). Resistance = 0.4286ohms and Current (I) = 7A
(b). Resistance (R) = 0.027 ohms and Current (I) = 111.1A
(c). Resistance (R) = 0.1071 ohms and Current (I) = 28A
Explanation:
From the question, given that;
ρ = 1.5*10-2ῼ.m
Lo = 7cm = 0.07m
V = 3V
From the formula R = ρL/A, where A is the area of cross section, L is the length of material and ρ is the resistivity.
(A)
L = 4Lo and A = 2Lo*Lo
R = ρL/A
R = ρ4Lo/(2Lo*Lo)
R = 2ρ /Lo = 2*1.5*10-2/0.07
R = 0.4286 ῼ
From this the current becomes;
I = V/R = 3/ 0.4286 = 6.99 = 7A
(B)
L = Lo and A = 4Lo * 2Lo
R = ρL/A
R = ρLo/ (4Lo*2Lo) after eliminating Lo from both sides we get,
R = ρ/8Lo = 1.5*10-2 / 8*0.07
R = 0.027
Current (I) = V/R = 3/0.027 = 111.1A
(C)
L = 2Lo and A = Lo * 4Lo
R = ρL/A
R = ρ2Lo/ (Lo*4Lo) eliminating Lo from both sides we get,
R = ρ/2Lo = 1.5*10-2 / 2*0.07 = 0.1071
The current becomes;
I = V/R = 3/0.1071 = 28A
Possibly, if you have list of densities and you have to match it. I can't think of any other scenarios in which it would be able to.
Hope I helped! :)
Newton's law of conservation states that energy of an isolated system remains a constant. It can neither be created nor destroyed but can be transformed from one form to the other.
Implying the above law of conservation of energy in the case of pendulum we can conclude that at the bottom of the swing the entire potential energy gets converted to kinetic energy. Also the potential energy is zero at this point.
Mathematically also potential energy is represented as
Potential energy= mgh
Where m is the mass of the pendulum.
g is the acceleration due to gravity
h is the height from the bottom z the ground.
At the bottom of the swing,the height is zero, hence the potential energy is also zero.
The kinetic energy is represented mathematically as
Kinetic energy= 1/2 mv^2
Where m is the mass of the pendulum
v is the velocity of the pendulum
At the bottom the pendulum has the maximum velocity. Hence the kinetic energy is maximum at the bottom.
Energy can neither be created e destroyed. It can only be transferred from one form to another. Implying this law and the above explainations we conclude that at the bottom of the pendulum,the potential energy=0 and the kinetic energy=294J as the entire potential energy is converted to kinetic energy at the bottom.
