Current And Voltage Measurements Multimeters can measure voltage,current and resistance in an electrical circuit.
It is very important to choose the correct range and to connect the multimeter leads properly.
Ohmic and Non-Ohmic Resistance Ohm’s Law –Ohmic resistance is constant over a wide range of voltages. –Non ohmic resistance varies with voltage Semiconductor diodes –One way valves for electricity 17.5, 226, 175
Electrical Activity In The Heart Muscle action is initiated by electrical activity Voltage pulses cause the heart to beat –These electrical waves travel through the body Monitored by electrocardiographs EKG (electrocardiogram) 177
If the atrial and ventricular contractions become irregular, we have fibrillation. –Defibrillators can be used to restore the normal heart rhythm 17.13
Cardiac Pacemakers Cardiac pacemakers may be implanted under the skin and attached with a wire to the right ventricle. –A lithium battery is used to charge a capacitor. It discharges 60 times per minute to stimulate the heart beat. If the heart is beating normally, the capacitor is not allowed to charge.
Cardioverter Defibrillators Implanted Cardioverter Defibrillators (ICDs) can monitor, record, process information, and send corrective signals to the heart. –The lithium batteries last 4 – 5 years. –Table 17.3 (Defibrillator Properties)
Electrical Activity In The Brain The brain produces electrical waves –Monitored by electroencephalographs EEG