4.2 Electrical Quantities

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?

	Filament lamp	Ohmic resistor
A	Q	S
B	R	Q
C	P	Q
D	Q	R

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?

	Charge	EMF
A	Q	E
B	C	V
C	A	J
D	J	ᘯ

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?

	current / A	direction of electron flow	direction of conventional current
A	7.00	Left to right	Right to left
B	3.43	Left to right	Right to left
C	7.00	Right to left	Right to left
D	3.43	Right to left	Right to left

A student connects a 6 V power supply to a 3 ᘯ resistor. The resistor is left connected to the power supply for 1 minute.

How much power is dissipated by the resistor?

A 3.0 ᘯ resistor is connected to a 15 V power supply as shown in the diagram. The ammeter reads 5 A throughout the experiment.

How much energy is dissipated as heat by the resistor in 2 minutes?

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

	X	Y
A	4.0	8.0
B	2.0	2.0
C	4.0	2.0
D	1.0	1.0

A student wants to measure the power dissipated by a 10 kᘯ resistor.

She (obviously) knows the resistance of the resistor. What other equipment is the minimum required to determine the power dissipated?

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.

	Change to length	Change to diameter
A	increase	increase
B	increase	decrease
C	decrease	increase
D	decrease	decrease

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?

	Length of wire / cm	Diameter of wire / mm
A	100	0.2
B	300	0.1
C	50	0.4
D	30	0.5