Topic 5 Electrical Circuits and Magnetism

The diagram shows a charged particle as it approaches a pair of charged parallel plates in a vacuum.
Which row describes the horizontal and vertical components of its motion as it travels between the plates? 

• A
• B
• C
• D

The resistance of a metal cube is measured by placing it between two parallel plates, as shown.
The cube has volume V and is made of a material with resistivity ρ. The connections to the cube have negligible resistance.
Which expression gives the electrical resistance of the metal cube between X and Y? 

• A
• B
• C
• D

Four resistors of equal value are connected as shown.
How will the powers to the resistors change when resistor W is removed? 

• The powers to X, Y and Z will all increase. 
• The power to X will decrease and the powers to Y and Z will increase. 
• The power to X will increase and the powers to Y and Z will decrease. 
• The power to X will increase and the powers to Y and Z will remain unaltered. 

Two positive point charges P and Q are held a certain distance apart.
At which point(s) could the electric field strength, due to the charges, be zero? 

• X only
• Y only
• Z only
• X and Z only

Two 6Ω resistors are connected in series with a 6V cell. A student incorrectly connects an ammeter and a voltmeter as shown. 
The readings on the ammeter and on the voltmeter are 

• A
• B
• C
• D

Which diagram best represents the electric field due to a negatively charged conducting sphere? 

• A
• B
• C
• D

A current carrying wire is in the same plane as a uniform magnetic field. The angle between the wire and the magnetic field is θ . 
The magnetic force on the current carrying wire is 

• zero. 
• into the plane of the paper. 
• out of the plane of the paper. 
• at an angle θ to the direction of the magnetic field. 

A charged particle of mass m and charge q is travelling in a uniform magnetic field with speed v such that the magnetic force on the particle is F. The magnetic force on a particle of mass 2m, charge q and speed 2v travelling in the same direction in the magnetic field is 

• 4F. 
• 2F. 
• F. 
• 1/2F. 

The tungsten lament of a lamp has a cross-sectional area A and length L.

For a potential difference V across the lament, the current in the filament is I.

The resistivity of the tungsten equals

• A

• B

• C

• D

Which of the following correctly gives the resistance of an ideal ammeter and resistance of an ideal voltmeter? 

• A
• B
• C
• D