Force and Torque exerted on a dipole system from a point charge

In summary, the conversation discusses a diagram showing three charges forming a dipole. The net force exerted on the dipole from a -10*10^-6C charge is found to be 1680N, and the torque exerted on the dipole by the same charge is 22.3N.m. The calculation for the force takes into account Coulomb's law and the distance between the charges, while the calculation for the torque considers the force and the perpendicular distance to the line of action.
  • #1
binbagsss
1,265
11
I have attached a diagram.
s
Three charge are at corners of an triangle. The + and - 5.00*10^-6C charges form a dipole.
a) Find the magnitude and direction of the force exerted on the dipole from the -10*10^-6C charge.
b) For an axis perepndiculat to the line connected the + and - 5.00*10^-6C charges , find the torque exerted on the dipole by the -10*10^-6 C charge, direction and magnitude?


My attempt:
a) The net force = 0.
Its magnitude on both charges = 1125 N, (from Coloumb's law and using r as 2cm.

However the answer is 1680N on both charges respectively.

b) Torque = Force * distance perpendicular to the line of action.

Considering a single charge, the force exerted on it is 1125N, and the distance perpendicular to the line of action 1.5cm.

The net torque will then = 2(1.5*10^-2 * 1125) , as the force acts in opposite directions on both charges, consequently rotating the dipole system in the same way.

T = 33.75N.m

(The correct answer is however 22.3N.m)F
 

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  • #2
The question is the force exerted on the whole dipole. You have to add the forces exerted on the separate charges, taking their directions into account.

ehild
 

Related to Force and Torque exerted on a dipole system from a point charge

1. What is a dipole system?

A dipole system is a pair of equal and opposite charges separated by a small distance. This creates a dipole moment, which is a measure of the system's polarity or strength of the electric field.

2. How does a point charge exert a force on a dipole system?

A point charge creates an electric field, which exerts a force on the dipole system. This force is proportional to the strength of the charge and inversely proportional to the distance between the point charge and the dipole system.

3. What is the torque exerted on a dipole system by a point charge?

The torque exerted on a dipole system by a point charge is the product of the electric field strength and the dipole moment. This torque causes the dipole to rotate until its orientation aligns with the direction of the electric field.

4. How is the direction of the torque determined?

The direction of the torque exerted on a dipole system is determined by the right-hand rule. If the fingers of the right hand curl in the direction of the electric field, the thumb points in the direction of the torque.

5. How can the force and torque on a dipole system be calculated?

The force and torque on a dipole system from a point charge can be calculated using Coulomb's Law and the definition of torque. The force can be calculated by taking the product of the point charge's strength and the electric field strength at the location of the dipole. The torque can be calculated by taking the cross product of the dipole moment and the electric field vector.

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