Electric & Magnetic Fields (HL IB Physics)

Two separated, identical conducting spheres X and Y of charge –8 μC and +12 μC respectively, are brought into brief contact and then separated.

What is the final charge distribution on X and Y?

Which of the following statements about electric fields and potential differences is incorrect?

A proton of mass m_p and charge q is accelerated from rest across a potential difference, V of 5 × 10^–2 V.

What is the best estimate for the magnitude of the proton’s final velocity, v_p?

A point charge q is placed near a large spherical charge Q = 10q.

What is the magnitude of the force experienced by q and Q and the magnitude of the electric field E created by Q at the position of q?

Two identical point charges q create a resultant electric field at X.

The line XY is a perpendicular bisector of the line joining both point charges.

Which vector most accurately depicts the direction of the resultant electric field at X?

Two charges, Q₁ = q and Q₂ = 4q are separated by a distance r and exert a force of magnitude F on each other.

By what factor does the magnitude of the force change if the charge on Q₁ doubles and the separation distance trebles?

A plotting compass is placed next to a vertical wire AB. When there is no current in the wire, the compass points North due to an external magnetic field.

Which diagram shows a possible direction for the compass to point when a current passes from A to B?

A potential difference is applied between two metal plates that are not parallel.

Which diagram shows the electric field between the plates?

Two point charges are at rest as shown. Four positions, each of distance r from the nearest point charge, are marked in the image. 

At which position is the electric field strength greatest?

A helium nucleus is accelerated from rest across a potential difference of 5.0 kV.

If m_p and m_n are the rest mass of a proton and neutron respectively, which expression for the final velocity of the nucleus is correct? 

Which diagram shows a correct equipotential line due to two point charges P and Q of equal sign? 

Four point charges, W, X, Y and Z, are fixed to the edges of a square with midpoint O.

W, X and Z are negatively charged, and Y is positively charged.

What is the direction of the resultant electric field at O?

The diagram shows equipotential lines around two sources. 

The possible sources of the field are:

1. two equal point charges of the opposite sign
2. two equal point charges of the same sign
3. two equal point masses

What are the only possible sources for the equipotential lines? 

A particle of charge q is at point J in a uniform electric field of strength E. The charge moves along a straight line from point J to point K which is at an angle of Φ to the field lines, as shown in the diagram below. 

If the length of the path is JK, what is the change in electric potential energy of the charge q between J and K? 

Two positively charged particles, q₁ and q₂, are released from rest half-way between two oppositely charged parallel plates in a vacuum. The particles strike the negatively charged plate at the same time. 

Neglecting gravitational effects, which of the following statements is correct? 

Two charged parallel metal plates, X and Y, are separated by a distance of 2.0 m. X is charged to a potential of –180 V and Y is charged to a potential of +180 V. 

What is the magnitude and direction of the electric field strength at a point exactly mid-way between plates X and Y? 

Point charges, each of magnitude Q are placed at three corners of a square as shown in the diagram.

What is the direction of the resultant electric field at the corner with no charge?

Which one of the following cannot be used as a unit for electric field strength?

What is the electric field pattern between a conducting sphere and an earthed metal plate?

Electric field strength is defined as 'the electric force per unit charge experienced by a small, positive point charge q'. 

Why is the test charge described as 'small'?

The electric potential at different points between two point charges is shown.

The electric field strength E varies along the line which connects P and Q.

Which graph correctly shows this variation, where x is the distance along the line PQ?

Point charges of +2.0 nC and −3.0 nC are arranged at the corners X and Y of a triangle with sides of 50 mm and 30 mm as shown. 

Which is the best estimate for the value of the ratio of the electric field at Z due to X and the electric field due to Y, ?

The diagram shows points X, Y and Z marked on a pattern of electric field lines. The spacing between X and Y and between Y and Z are the same.

The potential at X = 0 V and at Y is − 500 V.

What is a likely value for the potential at Z?

Two points charges of +4Q and –Q are placed 150 mm apart.

 Which of the following graphs shows the variation of the potential V against the distance x along the line joining the two point charges?

A positive charge is placed at S and a negative charge is placed at T. The electric potential at different points between the charges is shown below.

Which graph correctly shows the variation with x along the line ST of the electric field strength, E?

A weighted, positively charged sphere is released from rest, in a vacuum, between two parallel, vertical metal plates one at +100 V and the other grounded. The sphere is initially 4.0 cm from the edge of the grounded plate and 3.0 cm from the bottom of the plates. The sphere takes one of the paths P, Q, R or S and reaches the end of its trajectory in 60 ms.

By choosing the correct path, what is the speed of the sphere at the end of its trajectory?

The diagram shows a uniform electric field in which equipotential lines are placed 3.0 cm apart.

A charge of –6.0 nC is placed at the equipotential line X.

Which of the following statements is correct?

The diagram shows four point charges at the corners of a square of sides 4a.

What is the electric potential at P, the centre of the square?

A cable used in high-voltage electrical transmission has a radius of 3.0 mm. The diagram shows the circular cross-section of the cable with electrical field lines denoting areas of equipotential.

In the instant shown the potential of the cable is + 600 000 V.

Assuming that the diagram has been drawn to scale, what is the the potential gradient near the surface of the cable?

Two identical negative point charges, P and Q, are separated by a distance of 6.0 mm. The resultant electric potential at point M, which is mid–way between the charges, is –40 V.

What would be the resultant electrical potential at a point 2.0 mm closer to Q?