ELECTROMOTIVE FORCE AND POTENTIAL DIFFERENCE

EMF Power stations transfer energy from other forms into electrical energy Once this electrical energy has been created it can be used to power components. Only capacitors can store electrical energy Electromotive Force (e.m.f.) is the energy transferred per unit charge from one type of energy to electrical. Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

EMF e.m.f is measured in It is an expression of the maximum potential difference across the 1 volt = Mains electricity ( V) is therefore supplying each coulomb with J Derive the expression for e.m.f. Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

e.m.f tells us how much work is done on the charge Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

POTENTIAL DIFFERENCE Potential difference is the amount of energy transferred per unit charge from electrical energy to another form. V = W/Q Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

VOLTS What are both e.m.f and p.d measured in? An e.m.f. of 1V means that 1J of energy is transferred to every Coulomb of charge from the supply (cell, generator). A p.d. of 1V means that 1J of energy is transferred away from every Coulomb of charge to a component (buzzer, lightbulb). Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

VOLTS "emf' is the potential difference across a source of electricity when there is no current through the source. Close the circuit and current will flow but the cell may internally resist the flow. The potential difference seen across the terminals of the source will therefore be less than the potential difference when there is no current. Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

KIRCHOFF’S 2nd LAW By building a simple test circuit compare the e.m.f and p.d in both series and parallel circuits A V Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

KIRCHOFF’S 2nd LAW Investigate how current varies with potential difference in a series circuit with a fixed resistor. -Draw a results table which includes currents in both directions -Plot a graph of p.d. (x) against current (y). -Calculate the gradient. How does this relate to the value of resistance of your resistor? -How are V, I & R related? Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law

KIRCHOFF’S 2nd LAW Measuring e.m.f. & p.d. in a circuit – Conclusions: Series circuit – e.m.f. is equal to the sum of …. Parallel circuit – The e.m.f is equal to the... Describe the experiment that discovered the quantisation of charge State the definition of current Use Kirchoff’s First Law