Oxford Cambridge and RSA Examinations
Advanced Subsidiary GCE
PHYSICS A (2823/03/PLAN)
Practical Test (Part A - Planning Exercise)
Research/Theory
“The moment of a (turning) force about a given pivot is defined as follows.
Moment of a force = force x perpendicular distance from the pivot to the line of action of the force. The unit of moment is the Newton metre (Nm).”1
Also, “The principle of moments states that for any body in equilibrium, the sum of the clockwise moments about any pivot must equal the sum of the anticlockwise moments about that pivot.”1 (Fig. 1)
“Inside a solenoid, the magnetic field is uniform and its strength can be increased by increasing the current.”2
The principle of moments is used to find attractive force between the magnet and the solenoid.
The unknown force is the one produced with the bar magnet and solenoid. By using the equation of equilibrium previously given, the unknown force can be calculated provided that the system is in equilibrium: