Question

1. What is the resistance of a Nichrome^TM wire at 0.0 ∘C∘C if its resistance is 106.9 ΩΩ at 12.5 ∘C∘C? The temperature coefficient of resistivity for Nichrome^TM is 4.00×10⁻⁴ (∘C)−1(∘C)−1 .

Enter your answer with four significant figures.

2. A heart defibrillator is used to enable the heart to start beating if it has stopped. This is done by passing a large current of 12 AA through the body at 30 VV for a very short time, usually about 3.2 msms .

What power does the defibrillator deliver to the body?

Express your answer using two significant figures.

3. Electric eels generate electric pulses along their skin that can be used to stun an enemy when they come into contact with it. Tests have shown that these pulses can be up to 511 VV and produce currents of 80.0 mAmA (or even larger). A typical pulse lasts for 10.0 msms .

What power is delivered to the unfortunate enemy with a single pulse, assuming a steady current?

How much energy is delivered to the unfortunate enemy with a single pulse, assuming a steady current?

4. When a nerve cell depolarizes, charge is transferred across the cell membrane, changing the potential difference. For a typical nerve cell, 9.0 pCpC of charge flows in a time of 0.50 msms. What is the average current?

5. The biochemistry that takes place inside cells depends on various elements, such as sodium, potassium, and calcium, that are dissolved in water as ions. These ions enter cells through narrow pores in the cell membrane known as ion channels. Each ion channel, which is formed from a specialized protein molecule, is selective for one type of ion. When an ion channel opens in a cell wall, monovalent (charge ee) ions flow through the channel at a rate of 1.0×107ions/s1.0×107ions/s.

What is the current through the channel?

The potential difference across the ion channel is 70 mVmV. What is the power dissipation in the channel?

6. The filament of a 100 WW (120 VV) light bulb is a tungsten wire 0.035 mmmm in diameter. At the filament's operating temperature, the resistivity is 5.0×10−7Ω⋅m5.0×10−7Ω⋅m.

How long is the filament?

7. The average resistivity of the human body (apart from surface resistance of the skin) is about 5.0 Ω⋅mΩ⋅m. The conducting path between the right and left hands can be approximated as a cylinder 1.6 mm long and 0.10 mm in diameter. The skin resistance can be made negligible by soaking the hands in salt water.

What is the resistance between the hands if the skin resistance is negligible?

If skin resistance is negligible, what potential difference between the hands is needed for a lethal shock current of 100 mAmA? (Your result shows that even small potential differences can produce dangerous currents when the skin is damp.)

Answer 1

only first 4 questions can be solved at a time.