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Question

A 4.0 cm long straight wire carrying a current of 8A is placed perpendicular to a uniform magnetic field of strength 0.15 T. The magnetic force on the wire is __________ mN.

Magnetic Force Calculation on a Wire

The magnetic force ($F$) exerted on a straight wire carrying current ($I$) placed in a uniform magnetic field ($B$) is calculated using the formula:

$ F = I \times L \times B \times \sin(\theta) $

Where:

  • $I$ is the current in Amperes (A).
  • $L$ is the length of the wire in meters (m).
  • $B$ is the magnetic field strength in Tesla (T).
  • $\theta$ is the angle between the direction of the current and the magnetic field.

Given Values

From the question, we have:

  • Length of the wire, $L = 4.0 \text{ cm}$. We need to convert this to meters: $L = 4.0 / 100 = 0.04 \text{ m}$.
  • Current, $I = 8 \text{ A}$.
  • Magnetic field strength, $B = 0.15 \text{ T}$.
  • The wire is placed perpendicular to the magnetic field, so $\theta = 90^\circ$.
  • We know that $\sin(90^\circ) = 1$.

Applying the Formula

Substitute the values into the formula:

$ F = (8 \text{ A}) \times (0.04 \text{ m}) \times (0.15 \text{ T}) \times \sin(90^\circ) $

$ F = 8 \times 0.04 \times 0.15 \times 1 \text{ N} $

Calculating the Force

First, multiply the current and length:

$ 8 \times 0.04 = 0.32 $

Now, multiply the result by the magnetic field strength:

$ F = 0.32 \times 0.15 \text{ N} $

$ F = 0.048 \text{ N} $

Converting to MilliNewtons (mN)

The question asks for the force in milliNewtons (mN). To convert Newtons (N) to milliNewtons (mN), we multiply by 1000:

$ F = 0.048 \times 1000 \text{ mN} $

$ F = 48 \text{ mN} $

Final Answer

The magnetic force on the wire is 48 mN.

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