Answer:
(a) 
(b) 
Explanation:
(a) The surface current density of a conductor is the current flowing per unit length of the conductor.

Considering a wire, the current is uniformly distributed over the circumferenece of the wire.

The radius of the wire = a

The surface current density 
(b) The current density is inversely proportional
......(1)
k is the constant of proportionality

........(2)
substituting (1) into (2)





substitute 

-2. This is because it is gaining electrons. Electrons are negative. Therefore it is a negative charge.
Answer:
Explanation:
We shall apply concept of impulse to solve the problem .
Impulse = force x time
impulse = change in momentum
force x time = change in momentum
initial speed u = 24 km/h = 6.67 m /s
final speed v = 65 km/h = 18.05 m /s
change in momentum = m v - mu
= m ( v-u )
= 1350 ( 18.05 - 6.67 )
= 15363 kg m/s
F x 18 = 15363
F = 853.5 N .
Answer:
L = 0.635m
Explanation:
This problem involves the concept of stationary waves in pipes. For pipes closed at one end,
The frequency f = nv/4L for n = 1,3,5....n
For pipes open at both ends
f = nv/2L for n = 1,2,3,4...n
Assuming the pipe is closed at one end and that velocity of sound is 343m/s in air. If we are right we will obtain a whole number for n.
The film solution can be found in the attachment below.
Answer:
1. at least two charged interacting parts
2. from the electric fields of charged subatomic particles
3 an arrow released from the bow
4Electrical fields of charged particles interact, bonding those with opposite charges.
5 the interaction of the electric fields of protons and electrons
6 The energy stored in the system increases.
7 Kinetic energy increases because the magnets move in the direction of the field.
8 Iron pieces accelerate toward the magnet, and the energy stored in the system decreases.
9
The energy stored in the field decreases because the magnet moves in the direction of the field.
10 The energy stored increases and then decreases.
11 The wire was not connected to the source.
12 The electromagnet will become more powerful.
the rest are written, hope this helps (: