91Ó°ÊÓ

When talking about electricity, current is a fundamental concept. It's the flow of electric charge, and it can be calculated easily using Ohm's Law. Ohm's Law states that voltage (\( V \)) across a component equals the product of the current (\( I \)) flowing through it and its resistance (\( R \)). This can be expressed as:

• \( V = I \cdot R \)

Rearranging this formula will allow us to find the current:

• \( I = \frac{V}{R} \)

In the pacemaker exercise, the pacemaker generates a voltage of 6.0 V across the heart's resistance of 550 Ω. Substituting these values in, we calculate:

• \( I = \frac{6.0}{550} = 0.0109091 \) A (or 10.9 mA)

This shows how much current is flowing through the heart muscle during each pulse from the pacemaker.

Energy is another key aspect in electrical circuits, highlighting how much work is being done by the electric current. The energy (\( E \)) that transfers during a pulse can be calculated with:

• \( E = V \cdot I \cdot t \)

This formula tells us that energy depends on the voltage, the current, and the duration of time that the current flows. For our pacemaker, we already know:

• Voltage (\( V \)) = 6.0 V
• Current (\( I \)) = 0.0109091 A
• Time (\( t \)) = 0.65 ms = 0.00065 s

All these substituting into the energy equation give us:

• \( E = 6.0 \cdot 0.0109091 \cdot 0.00065 = 0.000042749 \) J

This means that each pulse delivers approximately 0.000042749 joules of energy to the heart muscle. Understanding this helps us appreciate how the pacemaker keeps the heart energized efficiently.

Power in an electrical context is all about the rate at which energy is used or transferred. It's how fast work is done, measured in watts. When calculating the average power (\( P \)) supplied by the pacemaker, we use the formula:

• \( P = \frac{E}{T} \)

Here, \( E \) is the energy delivered per pulse, and \( T \) is the time for one complete pulse. From the exercise, we found the energy per pulse to be 0.000042749 J. Since the pacemaker delivers 72 pulses per minute, the time for one pulse is:

• \( T = \frac{60}{72} = 0.8333 \) s

Plugging these into the power equation results in:

• \( P = \frac{0.000042749}{0.8333} = 0.000051314 \) W

This shows the average power output of the pacemaker, an important measure for ensuring the device operates effectively and efficiently to support the heart's needs.