Question

The magnetic field created by a long straight current carrying wire

A forms closed loops around the wire

B becomes weaker as the distance from the wire increases

C extends radially from the wire

D is parallel to the current in the wire and becomes weaker as the distance increases from the wire

E A and B are both correct

Answer 1

The magnetic field created by a long straight current-carrying wire forms closed loops around it and becomes weaker with increasing distance from the wire. The right choice is E, which states that both A (forms closed loops around the wire) and B (becomes weaker as the distance from the wire increases) are correct.

Step-by-step explanation:

The magnetic field created by a long straight current-carrying wire has specific characteristics. Firstly, magnetic field lines form closed loops around the wire, which is accurately described by the right-hand rule. As per this rule, if you point your right thumb in the direction of the current, your fingers will curl in the direction of the magnetic field loops. Secondly, the magnetic field strength decreases with the distance from the wire. The strength (B) of the magnetic field at a distance (R) from a long straight wire carrying current (I) is mathematically given by the equation B = μ0I/(2πR), where μ0 (mu-zero) represents the permeability of free space.

Therefore, when evaluating the statements given:

• A is correct as the magnetic field does form closed loops around the wire.
• B is correct because the magnetic field becomes weaker as the distance from the wire increases.
• C is incorrect because the field does not extend radially but in loops.
• D is incorrect since the magnetic field is not parallel to the current; it forms loops around the wire.

The correct answers to the question presented are E (A and B are both correct).

Answer 2

E) A and B are both correct

Step-by-step explanation:

The magnetic field created by a long straight current-carrying wire has specific characteristics. Let's discuss each option:

• A) Forms closed loops around the wire:

This is correct. According to the right-hand rule, the magnetic field lines around a straight current-carrying wire form concentric circles around the wire.

• B) Becomes weaker as the distance from the wire increases:

This is also correct. The strength of the magnetic field decreases with increasing distance from the wire. The magnetic field generated around a straight current-carrying wire is given as:

`\boxed{\left\begin{array}{ccc}\text{\underline{Magnetic Field Around Current-Carrying Wire:}}\\\\ \vec B = (\mu _0I)/(2 \pi r)\\\\\text{Where:}\\\text{$\bullet$ $B$ is the magnetic field strength (in Teslas, T)}\\\text{$\bullet$ $\mu _0$ is the permeability of free space ($4 \pi * 10^(-7) \ (Tm)/(A)$)}\\\text{$\bullet$ $I$ is the current flowing through the wire (in Amperes, A)}\\\text{$\bullet$ $r$ is the radial distance from the wire (in meters, m)}\end{array}\right}`

It is clear from the above equation that when 'r' increases, 'B' decreases.

• C) Extends radially from the wire:

This is incorrect. The magnetic field lines form loops around the wire, not radial lines extending from it.

• D) Is parallel to the current in the wire and becomes weaker as the distance increases from the wire:

This is incorrect. The magnetic field lines are not parallel to the current; they circle around the wire.

• E) A and B are both correct:

Since both A and B accurately describe the characteristics of the magnetic field around a long straight current-carrying wire, this is the correct answer.

Thus, (E) is correct.