Meters

Figure 131.

The magnitude force will change as the angle theta changes; the direction of the torque will reverse direction as the angle comes around past 90 degrees. Motors have multiple loops of wire so as to magnify the torque applied. Ultimately, it is the electrical energy that uses magnetism to drive the motor. This causes an oscillation of the coil with automatic switches referred to as brushes. The brushes will reverse the direction of the current in order to keep the torque going in the same direction.

METERS

These are represented by the analog fuel gauges in a vehicle and utilize magnetic torque on a current-carrying loop. The meter will have magnets that make the magnetic field proportional to the loop as much as possible. The meter is calibrated with a needle showing certain torques applied to the loop because the needle balances the torque on the loop. Only a small amount of revolution takes place on the pivot point, which leads to a change in the needle on the scale as is seen in figure 132: