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3 years ago

The radius of a conducting wire is doubled .What will be the ratio of its new specific resistance to the old one?

1 answer:

7 0

The equation for the resistance R is: R=ρ*(l/A), where, ρ is electrical resistivity, l is the length of the conductor, and A is the surface area.

The initial surface area is:

A=r²π, then when we double the radius we get:

A₁=(2*r)²π=4*r²π=4*A

Initial resistance is: R=ρ*(l/A).

When we double the radius, resistance is: R₁=ρ*{ l / (4*A) }

The ratio of the new resistance to the old one:

R₁/R=[ρ*(l/A)] / [ ρ* { l / (4*A) } ] = ρ, l and A cancel out and we get:

R₁/R=(1/1)/(1/4)=4/1

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Answer:

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Explanation:

Given:

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Spring potential energy is stored into potential energy,

$mg(h_{f} -h_{o}) = \frac{1}{2} kx^{2}$

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$k = \frac{2mg(h_{f} -h_{o} )}{x^{2} }$

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3 years ago

A large refrigerator (mass 80kg) sits at rest inside a house. The homeowner wants to move the refrigerator across the room, so s

Liono4ka [1.6K]

Answer:

400 N

Explanation:

By the law of friction,

$F=\mu R$

$F$ is the maximum frictional force, $\mu$ is the coefficient of friction and $R$ is the reaction on the refrigerator. On a horizontal surface, the reaction is equal to the weight of the refrigerator.

$R=mg$

$F=\mu mg$

While not moving, the fricition on the refrigerator is static friction. So, $\mu=0.65$

$F=0.65 \times80\times9.8=509.6 \text{ N}$

This is the maximum frictional force and is more than the applied horizontal force of 400 N. Frictional force cannot be more than the applied force, else it would actually pull the refrigerator backwards (a strange thing, if it were to happen). It is equal to the extent of the applied force because the applied force is not enough to overcome the maximum.

Hence the frictional force is 400 N.

PS: Note that we do not use the coefficient of kinetic friction because applied force could not overcome the static friction.

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It increases, because the centripetal acceleration is inversely proportional to the radius of the curvature.

Hopr it helps :)

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