This one has bothered me for a while (electric field)

In summary, there is a small charged sphere (A) and a larger sphere (B) made of a thin shell of nonconducting material. B is hanging from a non conducting, uncharged thread at a horizontal distance of 1.5m and an angle of 20 degrees from A, which has a charge of 120 microCoulombs. B has a radius of 0.05m and a mass of 0.025kg. The problem is to find the charge on B. One method is to use potential energy and electric field equations, but the length of the thread is unknown. Another method is to use forces and determine the tension in the cable, but this does not account for all forces on B.
  • #1
qz27
7
0
basically i have a small charged sphere on the left, and at a certain horizontal distance away from it there's a bigger sphere that is made of a thin shell of nonconducting material. the bigger sphere (B) is hanging from a non conducting, uncharged thread, and that thread makes an angle of 20 degrees with the vertical when sphere B is in equilibrium. centers of the sphere are at the same vertical height and are 1.5m away from each other.

the small sphere(A) has a charge of 120microCoulumns, and the larger sphere has radius of .05m and mass of .025kg

what is the charge on sphere B?
now i think if i set up an equation where the potential energy of sphere B ( since the thread hanging it is not vertical, B has a vertical displacement caused by the electric field b/t the two spheres) is equal to the electric field generated by the two spheres, i can figure out the charge on B. but i wasnt given the length of the thread, so that prevent me from getting the vertical displacement of sphere B.

but i wonder why the mass and radius of the sphere B was given tho..
any clue on where to tackle this problem?
 
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  • #2
I don't understand your method...

I'd just use forces... what are all the forces acting on the bigger sphere... The sphere is in equilibrium... so sum of forces in the x direction is 0... and sum of forces in the y-direction is 0. From that you can get the electrical force that the smaller charge exerts on the bigger... and from that you can get the charge.
 
  • #3
well, the force acting on the bigger sphere is just the repulsion force between the two spheres, but how can i find the electric field between them when i only know the charge of the smaller sphere?
 
  • #4
qz27 said:
well, the force acting on the bigger sphere is just the repulsion force between the two spheres, but how can i find the electric field between them when i only know the charge of the smaller sphere?

First find the tension in the cable... use sum of forces in the vertical direction.
 
  • #5
qz27 said:
well, the force acting on the bigger sphere is just the repulsion force between the two spheres
That does not account for ALL forces of sphere B.
 

1. What is an electric field?

An electric field is a region in space where an electrically charged particle experiences a force. It is created by a charged object and can exert a force on other charged particles within its influence.

2. How is an electric field measured?

An electric field is measured using a unit called volts per meter (V/m). This unit represents the amount of electric force (in volts) acting on a charge of one coulomb at a distance of one meter from the source of the field.

3. What is the difference between electric field and electric potential?

Electric field and electric potential are related but distinct concepts. Electric field is a measure of the force exerted by charged particles, while electric potential is a measure of the potential energy of a charged particle in an electric field. In simpler terms, electric field describes the strength of the force, while electric potential describes the amount of energy a charged particle would have at a certain point in the field.

4. How do you calculate the direction of an electric field?

The direction of an electric field is defined as the direction that a positive test charge would move if placed in the field. To calculate this direction, you can use the principle that electric field lines always point in the direction of the force on a positive test charge.

5. What are some real-life applications of electric fields?

Electric fields have numerous applications in our daily lives. They are used in electronic devices such as computers, televisions, and smartphones. Electric fields are also utilized in medical equipment such as MRI machines and defibrillators. Additionally, electric fields are used in power transmission and distribution to deliver electricity to homes and businesses.

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