Chapter 19 - DC Circuits

natural log

natural log

Where ξ is the voltage of the source, e is the base of the ________, R is the resistance of the resistor in the RC circuit, and C is the capacitance • The charge within a capacitor is given by Q= Q0 (1 − e−tRC) • Time COnstant- The product of resistance and capacitance in an RC circuit, represented by τ τ= RC • The voltage across a resistor in an RC circuit is calculated by VR= ξe −t /RC Thus current is ξe−t /RC I= R Capacitor Discharging • The voltage in a capacitor as it discharges is VC= V0e−t /RC • The charge as it discharges is Q= Q0e−t /RC Medical and Other Applications of RC Circuits • Sawtooth Voltage- A voltage whose graph resembles a saw blade • Electronic Pacemaker- A medical device that uses an RC circuit to deliver evenly spaced electrical pulses to the heart 19.7 Electric Hazards • Electric current running through the body may cause burns or stimulate nerves annd muscles • Ventricular Fibrillation- Occurs when a high current passes trhough the heart, it will cause irregular rhythms and blood is not properly pumped Safe Wiring • Power outlets contain 3 wires, the hot wire from which current flows, the neutral wire which carries away current, and the ground wire that connects to ground • Circuit Breakers- Devices that dtecte when too much current flows thruogh a wire, if the current passes over the threshold then it stops current from flowing • Leakage Current- Current that flows along an unintended path 19.8 Ammeters and Voltmeters- Measurement Affects the Quantity being Measured • Ammeter- A device that measures current • Voltmeter- A device that measures voltage • Galvanometer- An analog ammeter or voltmeter that works by using the force between a magnetic field and a current carrying coil How to Connect Meters • Ammeters must be connect directly within a circuit • Voltmeters are connect in parallel with the points between which voltage is being measured Effects of Meter Resistance • Sometimes, a meter can give a misleading reading • Voltmeters with high resistances compared to the circuit they are measuring have more accurate readings • The more sensitive a galvanometer is, the less its effect on the circuit is Other Meters • Multimeter- A meter that measure multiple electrical units • Ohmeter- A meter that measures resistance Digital Meters • Digital meters do not use a galvanometer but rather use semiconductor devices to measure • Their precision is extremely high, often around 0.01 %.

Source

Also called electromotive force, this is a device that provides electrical energy

EMF

The potential difference between two terminals of a source

Internal Resistance

The resistance within a source

Terminal Voltage

The voltage between two terminals

Series

Describe the connection between resistors when they are connected in a single path, end to end

Parallel

Describes connection in a circuit where the current branches off into multiple paths

Junction Rule

at any junction point, the sum of all currents entering the junction must equal the sum of all currents leaving the junction

Loop Rule

The sum of the changes in potential around any closed loop of a circuit must be zero

RC Circuit

A circuit containing both resistors and capacitors

Time Constant

The product of resistance and capacitance in an RC circuit

Sawtooth Voltage

A voltage whose graph resembles a saw blade

Electronic Pacemaker

A medical device that uses an RC circuit to deliver evenly spaced electricalpulses to the heart

Ventricular Fibrillation

Occurs when a high current passes trhough the heart, it will cause irregularrhythms and blood is not properly pumped

Circuit Breakers

Devices that dtecte when too much current flows thruogh a wire, if the currentpasses over the threshold then it stops current from flowing

Leakage Current

Current that flows along an unintended path

Ammeter

A device that measures current

Voltmeter

A device that measures voltage

Galvanometer

An analog ammeter or voltmeter that works by using the force between a magnetic field and a current carrying coil

Multimeter

A meter that measure multiple electrical units

Ohmeter

A meter that measures resistance