The problem involves two parts.
Firstly, you are asked to calculate the speed of the wire when pulled with a force of 1.3 Newtons. After that, you are asked to calculate the strength of the magnetic field.
Let's start with the speed of the wire.
To solve this part of the problem, you will need to apply the formula for mechanical power, which is work done per unit time, or force times velocity: P = F * v, where P is power, F is force, and v is velocity. In this case, you are given that the force applied is 1.3 Newtons and the power dissipated in the circuit is 4.2 Watts.
Since you are asked to find velocity (or in other words, the speed of the wire), you will need to rearrange the power equation to solve for v:
v = P / F
Substituting the given values into this equation:
v = 4.2 W / 1.3 N = 3.23 m/s
So, the speed of the wire is 3.23 m/s.
The second part of the problem asks for the strength of the magnetic field. Unfortunately, with the information provided (current, speed of the wire, and length of the wire), we cannot calculate the magnetic field strength. The calculation of the magnetic field strength needs additional parameters that are not given in the problem. Therefore, it's not possible to calculate this with the provided information.