current electricity essentials for exam

Question 1

what are the factors affecting resistance?

Answer 1

• -> material of the conductor
• -> length of the conductor
• -> thickness of the conductor
• -> temperature of the conductor

Question 2

how does the material of the conductor affect the resistance of the conductor

Answer 2

different materials have different concentration of free electrons and therefore the resistance of a conductor depends on its material

Question 3

how does resistance depend on the length of the conductor

Answer 3

directly proportional

Question 4

how does resistance depend on the thickness of the conductor

Answer 4

inversely proportional

Question 5

how does resistance depend on the temperature of the conductor?

Answer 5

directly proportional

Question 6

define electromotive force (E.M.F)

Answer 6

when no current is drawn from the cell (when the cell is in an open circuit)

then the potential difference between the terminals of the cell is called its EMF or electromotive force

Question 7

what is the formula for EMF?

Answer 7

EMF = work done / charge

Question 8

factors affecting the EMF of the cell

Answer 8

• -> The material of the electrodes

- -> The electrolyte used in the cell

Question 9

factors which DO NOT affect the EMF of the cell

Answer 9

• -> The shape of the electrodes
• -> Distance between the electrodes
• -> The amount of electrolyte in the cell

Question 10

define terminal voltage

Answer 10

when current is drawn from the cell (when the circuit is closed)

The potential difference between the electrodes of the cell is known as the terminal voltage

Question 11

differentiate between EMF and terminal voltage in terms of energy spent

Answer 11

–> EMF is defined as the energy spent in taking a positive test charge around the complete circuit (outside as well as inside)

–> Terminal voltage is defined as the energy spent in carrying a positive test charge around the circuit connected across the terminals of the cell (only outside the cell)

Question 12

define voltage drop

Answer 12

The work done per unit charge in carrying the positive test charge through the electrolyte

Question 13

define specific resistance

Answer 13

specific resistance of a conductor is the resistance of a material of unit length and area of cross section

Question 14

how does temperature affecting specific resistance

Answer 14

specific resistance increases with increase in temperature for metals

specific resistance decreases with increase in temperatures for semi conductors

Question 15

how does specific resistance vary from material to material

Answer 15

specific resistance is very high for insulators

specific resistance is low for semiconductors

specific resistance is very low for all metals