sci c13 🦭

• I = Q/T


  where current (I) is measured in amperes (A), charge (Q) is measured in coulombs (C) and time (t) is measured in seconds
• ammeter

  • used to measure the current flowing through an electric circuit. 

  • MUST be connected in series within a circuit

  • electrical symbol for the device as shown below

  
• potential difference

  • across a component in a circuit is the work done per unit charge in driving charges through the component

  • symbol is V
• V = W/Q

  where potential difference (V) is measured in volts (V), work done (W) is measured in joules (J) and charge (Q) is measured in coulombs (C)
• voltmeter

  • used to measure the potential difference across a component

  • MUST be connected in parallel with the component

  • electrical symbol is as shown below

  
• resistance

  • the resistance of a conductor is the ratio of the potential difference across it to the current flowing through it

  • symbol is R

  • unit is ohm
• R = V/I


  where resistance (R) is measured in ohms (), potential difference (V) is measured in volts (V) and current (I) is measured in amperes (A)
• resistors

  • electrical component that helps reduce the flow of current in a circuit

  • TWO types

  > fixed : fixed and non-adjustable resistance

  > variable : adjustable resistance ranging from 0 to a certain value

  • pic shows both respectively

  
• resistance ( big idea )

  • resistance opposes the flow of current.

  • as the resistance in a circuit increases, the current flowing in the circuit decreases, and vice versa.

  • the current flowing through the battery is dependent on the total resistance of the circuit.
• calc the total resistance

  • need to calculate total resistance of the circuit if there are more than 1 resistor

  • total resistance is also known as effective resistance

  • to calculate total resistance, it depends on the arrangement of resistors.
• resistors in series 


  • total resistance is equal to the sum of the individual resistances

  • total resistance of resistors is greater than the largest individual resistance

  • calc = total resistance = r(1) + r(2) ++

  
• resistors in parallel


  • total resistance of resistors is smaller than the smallest individual resistance.

  • calc : total resistance = (1/r1+ 1/r2++) ^-1

  
• relationship between current and potential difference in series

  • the components are connected one after another in a single loop.

  
• relationship between current and potential difference in series

  • as the electric current has only one path to flow through, the current flowing through each component is the same.

  • the p.d. supplied by the battery is equal to the sum of the p.d. across each component.

  • relationship between the total resistance and individual resistance of each components in a series circuit

  
• relationship between current in parallel

  •, the components are connected to the battery in 2 or more loops (one after another in a single loop).

  • there is more than one path through which the current can flow. • the current I from the battery splits into I1 and I2.

  • hence the current from the battery is the sum of the individual current in each parallel branch.

  
• relationship between potential difference in parallel

  • The p.d. supplied by the battery is equal to the p.d. across each parallel branch.

  
• electric charge

  • when an electrical circuit is closed, electric charge flows through the circuit in one direction.

  • symbol : Q

  • measured in coulombs (C)
• electric current

  • is the rate of flow of electric charge

  • symbol : I

  • unit : amperes (A)