4.3 Electrical circuits

• Kirchhoff's second law

  $\Sigma\epsilon=$$\Sigma V$
• Kirchhoff's second law

  Sum of the pds in a circuit is equal to the sum of the emfs;

  Total energy tranferred to the charges is equal to the total charges transferred from the charges due to the conservation of energy
• Voltage in series circuits is split proportionately amongst components
• internal resistance is the resistance of a source of emf due to its construction which causes a loss in energy / voltage as the charge passes through the source
• Resistance of the materials in the cell cause internal resistance in a battery - some energy is lost (transferred to heat) when there is a current
• Lost volts = emf - terminal pd
• terminal pd is the pd measured across the terminals of the battery / cell
• emf > terminal pd
• Lost volts increase when current is high as more charges travel through the cell each second so more work is done by the charges, increasing the lost volts
• The output of a potential divider circuit drops when it is loaded (has a component connected across it in parallel) as, unless the component has an infinite resistance, the overall resistance decreases, meaning its proportion of the emf decreases