electricity chp 9

Question 1

electric current

Answer 1

the rate of flow of charge in a wire/component

Question 2

charge

Answer 2

a property of matter and can be positive and negative

Question 3

conventional current

Answer 3

current flowing from positive side to negative side

Question 4

power

Answer 4

the transfer of energy

Question 5

resistance

Answer 5

blockage of the movement of electrons

Question 6

joule heating

Answer 6

the heating effect of when a current passes through a resistor

Question 7

ohm’s law

Answer 7

for a metallic conductor at room temp, the current is proportional to the potential difference across it

Question 8

resistivity

Answer 8

property that describe the extend to which a material can oppose to the flow of electric current

Question 9

use of thermistor

Answer 9

resistor that is sensitive to high temperatures

Question 10

EMF

Answer 10

Energy transferred by a source per unit charge around a complete circuit

Question 11

Potential difference

Answer 11

Energy transferred per unit charge as it passes through a component

Question 12

Forward bias

Answer 12

Positive voltage across diode, allowing current to flow

Question 13

Reverse bias

Answer 13

Negative voltage across diode, blocking current flow

Question 14

Reverse bias

Answer 14

Potential diff switched, negative voltage across diode

Question 15

Difference between EMF and PD

Answer 15

• emf measured in open circuit, pd in closed
• emf is cause of pd, pd is effect of emf
• emf no energy loss, pd yes energy loss (resistance)

Question 16

I-V characteristic of metallic conductor at constant temp

Answer 16

• follows ohm’s law
• I-V graph is straight line (constant resistance)
• slope represents resistance
• only linear when temp is constant (inc temp, inc resist)

Question 17

I-V characteristic of semiconductor diode

Answer 17

• doesn’t follow ohm’s law
• in forward bias, current remains small until voltage reaches threshold
• in reverse bias, small leakage of current flows until breakdown od voltage is reached
• graph is highly asymmetric with significant current flowing only in forward direction after threshold voltage is surpassed

Question 18

Why do diodes not follow ohm’s law

Answer 18

• current stays small until voltage reaches a certain level, then increases quickly
• current can only flow in one direction
• variable resistor