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6. Figure 20.11 shows an experimental set-up that uses a beam balance to measure the strength of a magnetic field B. The beam balance is pivoted at its midpoint, and standard masses $m_1$ and $m_2$ are placed on the left and right pans respectively. The bottom part of the right pan is connected to a rectangular wire loop of N turns. A current I is flowing inside the loop in a clockwise direction, and three-quarters of the wire loop is in a uniform magnetic field with magnetic field strength B such that the beam balance is horizontal. Figure 20.11 When the direction of the magnetic field is reversed, the beam balance tilts to the left. Extra mass m has to be added to $m_2$ in order to balance the beam balance again. The magnitude of the resultant electromagnetic force, F, acting on the wire loop can be expressed as: $F = NBIL$ (a) Deduce the direction of the magnetic field in Figure 20.11. (b) Show that $m_1$ is equal to $(m_2 + \frac{F}{g})$, where g is the gravitational field strength. (c) Deduce the direction of the electromagnetic force F when the magnetic field is reversed. (d) Using the information given and answers in (a) and (b), show that the magnetic field strength B can be expressed as: $B = \frac{mg}{2NIL}$

          6. Figure 20.11 shows an experimental set-up that uses a beam balance to measure the strength of a magnetic field B. The beam balance is pivoted at its midpoint, and standard masses $m_1$ and $m_2$ are placed on the left and right pans respectively. The bottom part of the right pan is connected to a rectangular wire loop of N turns. A current I is flowing inside the loop in a clockwise direction, and three-quarters of the wire loop is in a uniform magnetic field with magnetic field strength B such that the beam balance is horizontal.

Figure 20.11

When the direction of the magnetic field is reversed, the beam balance tilts to the left. Extra mass m has to be added to $m_2$ in order to balance the beam balance again.

The magnitude of the resultant electromagnetic force, F, acting on the wire loop can be expressed as:

$F = NBIL$

(a) Deduce the direction of the magnetic field in Figure 20.11.
(b) Show that $m_1$ is equal to $(m_2 + \frac{F}{g})$, where g is the gravitational field strength.
(c) Deduce the direction of the electromagnetic force F when the magnetic field is reversed.
(d) Using the information given and answers in (a) and (b), show that the magnetic field strength B can be expressed as: $B = \frac{mg}{2NIL}$

6 figure 2011 shows an experimental set up that uses a beam balance to measure the strength of a magnetic field b the beam balance is pivoted at its midpoint and standard masses m1 and m2 46296

Added by Timothy L.

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