# Kirchhoff's Laws and Circuits

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• Kirchhoff's Laws and Circuits
• Kirchhoff's laws
• First law
• The sum of the current entering a junction is equal to the sum of the current exiting a junction
• The law of conservation of charge applied to electric circuits
• Second law
• The sum of the E.M.F. is equal to the sum of the P.D. in a closed loop
• Series circuits
• There is a single loop from one terminal of the source of E.M.F. to the other
• The current is the same in every position
• E.M.F. is shared between the components
• If components have the same resistance, E.M.F. is shared equally
• If components have different resistances, E.M.F. is shared proportionally
• Parallel circuits
• Provide more than one path for charges
• The amount of charge down a path depends on the resistance of the path
• The greater the resistance, the less current flows down it
• Total E.M.F. around each separate loop in a parallel circuit is equal to the E.M.F.
• Each loop can be thought of a a separate circuit- changes to one branch doesn't affect the others
• Multiple loops and adding components
• In more complex circuits, consider each loop separately
• Adding additional components in series reduces the E.M.F. shared between the original components