In 1 hour, the hour hand sweeps across 1/12 of the clock's face. In 40 min, the hour hand travels (40 min)/(60 min) = 2/3 of the path it covers in an hour, so a total of 1/12 × 2/3 = 1/18 of the clock's face. This hand traces out a circle with radius 0.25 m, so in 40 min its tip traces out 1/18 of this circle's radius, or
1/18 × 2<em>π</em> (0.25 m) ≈ 0.087 m
The minute hand traverses (40 min)/(60 min) = 2/3 of the clock's face, so it traces out 2/3 of the circumference of a circle with radius 0.31 m:
2/3 × 2<em>π</em> (0.31 m) ≈ 1.3 m
The second hand completes 1 revolution each minute, so in 40 min it would fully trace the circumference of a circle with radius 0.34 m a total of 40 times, so it covers a distance of
40 × 2<em>π</em> (0.34 m) ≈ 85 m
Explanation:
For this problem we have to take into account the expression
J = I/area = I/(π*r^(2))
By taking I we have
I = π*r^(2)*J
(a)
For Ja = J0r/R the current is not constant in the wire. Hence

and on the surface the current is

(b)
For Jb = J0(1 - r/R)

and on the surface

(c)
Ja maximizes the current density near the wire's surface
Additional point
The total current in the wire is obtained by integrating

and in a simmilar way for Jb
![I_{T}=\pi J_{0} \int\limits^R_0 {r^{2}(1-r/R)} \, dr = \pi J_{0}[\frac{R^{3}}{3}-\frac{R^{2}}{2R}]=\pi J_{0}[\frac{R^{3}}{3}-\frac{R^{2}}{2}]](https://tex.z-dn.net/?f=I_%7BT%7D%3D%5Cpi%20J_%7B0%7D%20%5Cint%5Climits%5ER_0%20%7Br%5E%7B2%7D%281-r%2FR%29%7D%20%5C%2C%20dr%20%3D%20%5Cpi%20%20%20J_%7B0%7D%5B%5Cfrac%7BR%5E%7B3%7D%7D%7B3%7D-%5Cfrac%7BR%5E%7B2%7D%7D%7B2R%7D%5D%3D%5Cpi%20J_%7B0%7D%5B%5Cfrac%7BR%5E%7B3%7D%7D%7B3%7D-%5Cfrac%7BR%5E%7B2%7D%7D%7B2%7D%5D)
And it is only necessary to replace J0 and R.
I hope this is useful for you
regards
Answer:
Explanation:
1) TRUE; potential difference can be calculated using path integral. Since the electric field is a conservative, the potential difference can be calculated using any path.
2) TRUE; since potential due to a charge is inversely dependent on distance, at infinity the potential will be almost zero.
3) TRUE, W = q.VBA.
4) FALSE; eV is a unit for work (or) energy.
5) TRUE; since the electric force is conservative force. There will be no loss in energy, the decreased potential energy will be coverted to kinetic energy.
6) FALSE; in the direction of electric field the potential decreases.
7) FALSE; equipotential surface is perpendicular to the electric field lines.
8) FALSE; electrostatic potential is scalar quantity. It depends only on the charge and distance from it.
9) FALSE; Inside a conductor the electric field is zero but the electric potential is constant at the value that is at the surface of the conductor.
10) TRUE; as long as the field is being measured outiside the body the bodies act as point charges. So electric fields due to all types of bodies charged identically will be equal.