L2 Physical Science Electric Circuits 1

Lecturer: Semase M.P Physical Science L2 Downloaded Sefikeng Campus from hlayiso.com

Subject outcome Identify, describe and apply the principles of an electrical circuit Learning outcomes  Define and calculate electrical current in terms of the rate of the number of charges  Differentiate between two types of current in terms of use, source and current flow  Describe electrical safety and groundings  Describe resistors in terms of resistance in terms of resistance due to length, width and material used for load  Describe and identify the relationship between load and current seek patterns  Investigate the relationship between resistance of globe and brightness of globe Downloaded from hlayiso.com

Introduction • A series circuit has only one path for electrical current to flow. The current is the same everywhere in a series circuit. The total potential difference, however, is the sum of potential difference through the circuit. • In a parallel circuit, there is more than one path for the current to flow. The current divides in each branch of the cycle. The potential difference is the same across parallel connectors. Downloaded from hlayiso.com

Electrical circuits Series circuit Parallel circuit Downloaded from hlayiso.com

Principles of current in a circuit • The current in a series circuit is the same at all points • In a parallel circuit, the current divides according to the resistance in each branch • The total current entering the branch is the same as the total current leaving • Current is measured with an ammeter connected in series Downloaded from hlayiso.com

Safety device in electrical equipment Grounding fuses • Grounding is a way of ensuring • Fuses are used in appliances to the safety of electrical prevent too much current appliances. from flowing the appliance • Work through a ring main so • If excess current flows through that if there is a fault in the the fuse it overheats and melts wiring charges do not reach the case • Circuit breaks and no current flows • If a faulty appliance is not • When you charge a fuse you earthed you can be need to check what the electrocuted if you touch it current marking on the fuse is Downloaded from hlayiso.com

Causes of electrical faults • Incorrect usage- getting appliances wet and having cables wound up • Overloading- having many appliances connected to the same circuit • Damage- wires such as fraying • An open circuit- which occurs when there is break in the circuit so no current will flow Downloaded from hlayiso.com

Resistors • Resistors are devices that resist electrical current. The level of resistance depends on the thickness and material that the resistor is made out of. • The part of the circuit on which work is done is called the load. There is a relationship between load and current-seek patterns • In a circuit, the higher the load, the smaller the current. Downloaded from hlayiso.com

Summary • Electrical circuit is the flow of charge from one terminal of a battery to the other • Current always seek the least resistance in a circuit • Electrical potential difference is the measure of the energy given to each coulombs of charge leaving the cell • A current of one ampere flows through a point in a circuit when the quality of charge passing through that point is one second • Resistance of a wire increases with length, and decreases with the thickness of the wire. Downloaded from hlayiso.com

Assessment activity • Draw a circuit of two bulbs in a series and three cells in series, an ammeter and a closed switch.(5) • Why is it dangerous to touch an electrical appliance when standing in water(3) • Why should you not use a mains electric mower with the cable coiled up (2) • Are the coils connected in series or in parallel(2) Downloaded from hlayiso.com