Electrical Quantities (Cambridge O Level Physics)

Four current-voltage graphs are given below.

One of them is for an ohmic resistor, and another is for a filament lamp.

Which is which?

Which of the diagrams below shows the correct electric field pattern for oppositely charged parallel plates?

Which row in the table gives the correct units for charge and for EMF?

A student sets up a circuit as shown in the diagram

A charge of 4.9 C flows through the lamp in 0.7 s.

What is the current through the resistor, which direction do electrons flow through the resistor, and what is the direction of the conventional current through the resistor?

Which row in the table shows possible values for the two meters shown in the circuit diagram?

A student wants to charge up some rods by rubbing them with a cloth made from a suitable material.

He has a number of rods to choose from: a copper rod, a PVC rod, an aluminium rod and a glass rod.

Which two of the rods would hold a charge when rubbed with an appropriate cloth?

A student muses on the concept of the resistance of a wire.

She wonders whether changing the diameter of the wire and the length of the wire would affect the resistance.

Since you have studied this in physics, you know the answer!

Choose the row from the table in which changes are made to both the diameter and the length that would each decrease the resistance of a wire.

A student rubs a polythene rod with a cloth, giving it a negative charge. She then holds it near an earthed, conducting sphere as shown in the diagrams below.

Which of the diagrams shows the correct distribution of charges on the conducting sphere?

A student has four copper wires, of different dimensions.

Which of her wires has the largest resistance?

The diagram shows an uncharged ball covered with metallic paint. The ball is suspended from an insulating thread. It is placed near a positively charged rod.

Which diagram shows the charge distribution on the ball?

A charge of 45 C flows through an electric appliance in 3.0 minutes.

What is the average current in the appliance?

A wire of length 0.50m and cross-sectional area 1.0 × 10^–6m² has a resistance of 0.75 Ω.
Another wire of the same material has a length of 2.0 m and a cross-sectional area of 0.50 × 10^–6m².
What is the resistance of the longer wire?

Which diagram shows the pattern and direction of the electric field lines near a positive charge? 

A positively charged rod is held close to an insulated metal sphere. The sphere is earthed as shown. 

The earth connection is removed and then the rod is removed. 

Which diagram shows the charges on the sphere after the rod is removed? 

The diagram shows an electrostatic precipitator. It can be used to remove dust from air.

What happens at the negative grid?