26 Questions
What is the unit of electric charge?
Coulomb (C)
What happens when like charges interact with each other?
They repel each other
Name three uses of the gold leaf electroscope.
To detect small charges, estimate the size of a charge, identify the sign of the charge, and distinguish between a conductor and insulator
What is the result of rubbing cloth against polythene?
The polythene becomes negatively charged
What is the characteristic of a conductor in terms of electric charge?
Electric charge can flow through it
Where do static charges reside on a conductor?
On the outside of the conductor
What is the effect of point discharge on a sharp point?
A strong electric field is created
What happens when ions are brought near a neutral object?
They are attracted and repelled, neutralizing the object
What is the effect of the 'electric wind' on a naked flame?
It is demonstrated by the effect of the 'electric wind' on a naked flame
What is an insulator?
A substance that does not allow current to flow through it
What is the significance of the shape of a conductor in relation to the accumulation of static charge?
Static charge on a conductor tends to accumulate where the conductor is most pointed.
Point discharge occurs at a sharp point due to what?
High charge density
Where does electric charge reside on a conductor?
On the outside of the conductor
Why are elecricity industry workers safe to work on power lines while wearing full body conducting suits?
Because electric charge resides on the outside of a conductor
What happens when a cloth is rubbed against polythene and against perplex?
The polythene becomes negatively charged, and the perplex becomes positively charged.
Why does a strong electric field get created at a very sharp point?
This is because point discharge occurs at a very sharp point due to charge density, resulting in a strong electric field.
What is the relationship between the electrostatic force and the distance between two point charges, according to Coulomb's Law?
The electrostatic force is inversely proportional to the square of the distance between the two point charges.
What is the role of the permittivity of the medium (ε) in Coulomb's Law?
The permittivity of the medium (ε) is a factor that affects the electrostatic force between two point charges, and it depends on the properties of the medium in which the charges are placed.
What happens to the electrostatic force between two point charges if the distance between them is tripled?
The electrostatic force will be reduced to one-ninth of its original value.
What is the effect of increasing the charge on one of the point charges on the electrostatic force between them, assuming the distance between them remains constant?
The electrostatic force will increase in proportion to the increase in the charge.
What is the significance of the product of the charges (Q1 Q2) in Coulomb's Law?
The product of the charges (Q1 Q2) determines the magnitude of the electrostatic force between the two point charges.
What is the direction of a positive charge if it is placed in an electric field?
Along the electric field line
What is the electric field strength at a point in an electric field?
The force per unit positive charge at that point
What is the formula for electric filed strenght?
E = F/C
What is the S.I. unit of electric field strength?
Newton per coulomb (N C-1) or volt per meter (V m-1)
What is the formula for electric field strength in terms of charge and distance?
E = Q / 4πεd^2
Study Notes
Electric Charge
- Electric charge (Q or q) indicates if a body has more or less electrons than protons.
- The unit of charge is coulomb (C).
- An atom is made up of three particles: protons, neutrons, and electrons.
- Protons and neutrons are located in the centre of the atom, and electrons orbit the nucleus.
Properties of Charges
- Like charges repel each other.
- Unlike charges attract each other.
Conduction and Insulation
- A conductor is any substance through which electric charge can flow.
- An insulator is any substance through which electric charge cannot flow.
- All static charges reside on the outside of a conductor.
- Static charge on a conductor tends to accumulate where the conductor is most pointed.
Point Discharge and Ions
- Point discharge occurs at a very sharp point due to charge density, resulting in a strong electric field being created.
- Ions are both attracted and repelled, neutralising the object.
Gold Leaf Electroscope
- The gold leaf electroscope is used to detect small charges, estimate the size of a charge, identify the sign of the charge, and distinguish between a conductor and insulator.
- It consists of multiple components, most importantly a thin gold leaf placed close to a metal rod.
- If the gold leaf and metal rod are charged with the same sign, they repel each other.
Coulomb's Law
- The force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
- F = 1/4πε x (Q_1 Q_2)/d^2, where F is the electrostatic force, ε is the permittivity of the medium, Q_1 and Q_2 are the charges, and d is the distance between the charges.
Electric Field
- An electric field is any region of space where a static electric charge experiences a force other than the force of gravity.
- An electric field line is the line along which a positive charge would move if placed in the electric field.
- The electric field strength (E) at a point in an electric field is the force per unit positive charge at that point.
- S.I. Unit = newton per coulomb (N C^-1) or volt per meter (V m^-1).
- E = F/Q, where E is the electric field strength, F is the electrostatic force, and Q is the charge on the body placed in the electric field.
- E = 1/4πε Q/d^2, where E is the electric field strength, Q is the charge on the body, ε is the permittivity of the medium, and d is the distance from the charged body.
Test your understanding of static electricity and electric charge, including the structure of an atom, types of charges, and how they interact. Learn about the unit of charge, coulomb, and how rubbing certain materials can cause a change in charge.
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