5- Charge And Current

Question 1

Charge

Answer 1

• Opposite charges attract each other
• Similar charges repel
• Static electricity can be produced by rubbing insulators together to move electrons forcibly

Question 2

Equations for current

Answer 2

• I (A)=change in charge/change in time
• change in charge (C)=I×change in time
• C = quantity of charge
• Charge on an electron is 1.6×10^-19
• I = Coulombs per second

Question 3

Measuring current

Answer 3

• Ammeters have negligible resistance in order to monitor current speed without affecting it
• In series circuits, current is equal across all components as a result of charge conservation
• In parallel circuits current varies across different branches of a circuit, but the total of all the current across all the branches must be the same as the current outputted by the power supply
• Branches with lower resistance have greater currents across them

Question 4

Drift velocity formula

Answer 4

• I=QnAV
• Q= charge in each carrier (C)
• n = no. Charge carriers per m^3 (m^-3)
• A= Cross sectional area of conductor (m^2)
• V= drift velocity of carriers (ms^-1)
• I= current across conductor (Cs^-1)

Question 5

Conductors and semi-conductors

Answer 5

• conductors commonly have de-localised electrons that carry charge (hence called charge carriers)
• these electrons regularly collide with the positive metal ions, slowing them down and creating a constant drift velocity rather than continuous acceleration
• semi-conductors release more de-localised electrons when they gain energy through either light (photovoltaic cells) or heat, etc