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Circuits, Currents & Magnets. Here is a simple electric circuit. It has a cell, a lamp and a sw itch Remember an electric current is measured in Amps or Coulombs/Seconds. I = q/t Current = charge / time. Ammeter.
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Here is a simple electric circuit. It has a cell, a lamp and a switch • Remember an electric current is measured in Amps or Coulombs/Seconds. • I = q/t • Current = charge / time
Ammeter Electric current (how fast the current is moving)is measured using an ammeter connected in series in the circuit A
How is AMPs (current) measured? SERIES CIRCUIT 2A • current is the same • at all points in the • circuit. 2A 2A PARALLEL CIRCUIT 2A 2A • current is shared • between the • components 1A 1A
Example problem • What charge (q) flows in a section of a copper wire in 32seconds if the ammeter measures a current of .8A ? Hint: • I = q/t (don’t forget units)
Problem #1 • What charge flows in a cross section of a wire in 10 minutes if the ammeter measures a current of 5mA ? A
Voltmeter Voltage (how much power is capable of coming out of this devise of area)The bigger the voltage supplied by the cell, the bigger the current. V
In a series circuit • Unlike an ammeter a voltmeter is connected across the components.Voltage is shared between the components 3V 1.5V 1.5V
And In Parallel circuit • voltage is the same in all parts of the circuit 3V 3V 3V
Problem A • Solve the unknown Amps = #1,2? V =#1,2? a) 6V 4A A1 V1 V2 A2
Problem B • Solve the following Amps #1,2,3? V= #1,2? b) 6V 4A A1 V1 A2 V2 A3
Resistors in series circuits • the equivalent (total)resistance, • the total current from the power supply, • the current through each resistor, • the voltage drop across each resistor, and • the power dissipated in each resistor.
Total current is determined by the voltage of the power supply and the equivalent resistance of the circuit. IT = VT/RT = 125 V/100 Ω = 1.25 A
Verify your calculations by adding the voltage drops. On a series circuit they should equal the voltage increase of the power supply
What is the power for the other 2 resistors? • P1 = V1I1 = (25.0 V)(1.25 A) = 31.250 W
Resistances in parallel ; combine according to the sum-of-inverses rule
Total current is determined by the voltage of the power supply and the equivalent resistance of the circuit. • IT = VT/RT = 125 V/12.5 Ω = 10 A
On a parallel circuit, each branch experiences the same voltage drop • VT = V1= V2 = V3 = 125 V
On a parallel circuit they should add up to the current from the power supply.
batteries • There are two kinds of batteries: dry cell and wet cell batteries. Here is an example of a dry cell • The zinc container of the dry cell contains a moist chemical paste surrounding a carbon rod suspended in the middle.
Wet cell batteries are most commonly associated with automobile batteries A wet cell contains two connected plates made of different metals or metal compounds in a conducting solution. Most car batteries have a series of six cells, each containing lead and lead oxide in a sulfuric acid solution.
The earth is like a giant magnet! The nickel iron core of the earth gives the earth a magnetic field much like a bar magnet.
What is a magnetic domain? • Magnetic substances like iron, cobalt, and nickel are composed of small areas where the groups of atoms are aligned like the poles of a magnet. These regions are called domains. All of the domains of a magnetic substance tend to align themselves in the same direction when placed in a magnetic field. These domains are typically composed of billions of atoms.
How are magnetic fields and electricity connected? When an electric current passes through a wire, a magnetic field is formed.
Electromagnet When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.
