the average blood velocity is 20.0 cm/s? 3. Estimate magnetic field strength 1 mm away from the axon if magnitude of axon current is I = 4.1×10 A. Suppose, that axon is long straight current caring wire. Magnetism.pdf MAGNETIC FIELD. MAGNETISM IN NATURE 1. The magnitude of the magnetic force F on a charge q moving at a speed v in a magnetic field of strength B is given by F = qvBsin0, where 0 is the angle between the directions of v and B. This force is often called the Lorentz force. In fact, this is how we define the magnetic field strength B in terms of the force on a charged particle moving in a magnetic field. The SI unit for magnetic field strength B is called the tesla (T). 2. Force on a moving charge in a magnetic field. Magnetic force can cause a charged particle to move in a circular or spiral path. In this case, the magnetic force supplies the centripetal force. mv? = qvB, here, r is the radius of curvature of the path of a charged particle with mass m and charge q , moving at a speed v perpendicular to a magnetic field of strength B (0 = 1) . 3. The Hall Effect The magnetic field also affects charges moving in a conductor. Figure 1 shows what happens to charges moving OB (out of paper) RHR-1 F. through a conductor in a magnetic field. The field is perpendicular to the electron drift velocity and to the width (a) i O of the conductor. Note that conventional current is to the right in both parts of the figure. In part (a), electrons carry the current and move to the left. In part (b), positive charges carry the current and move to the right. Moving electrons feel a magnetic force toward one side of the conductor, leaving a net positive charge on the other side. This separation of charge creates a voltage ɛ , known as the Hall emf, across the conductor. The creation of a voltage across a current-carrying conductor by a magnetic field в (b) -E O F. is known as the Hall effect: qE = qvB, or E = vB. Note that the electric field E is uniform across the conductor because the magnetic field B is uniform, as is the conductor. For a uniform electric field, the relationship between electric field and voltage is E = ɛ/l , where l is the width of the conductor and ɛ is the Hall EMF. Entering this into the last expression gives ɛ = Blv where ɛ is the Hall effect voltage across a conductor of width I through which charges move at a speed v. The Hall effect can be used to measure fluid flow in any fluid having free charges, such as blood. 4. Magnetic force on a current-carrying conductor F = IlBsin0, here F is magnetic force on a length 1 of wire carrying a current I in a uniform magnetic field B. 5. The torque t on a current-carrying loop of any shape in a uniform magnetic field is t = NIABsin0, where N is the number of turns, I is the current, A is the area of the loop, B is the magnetic field strength, and O is the angle between the perpendicular to the loop and the magnetic field. 6. The magnetic field strength (magnitude) produced by a long straight current-carrying wire is found by experiment to be B = 20, where I is the current, r is the shortest distance to the wire, and the constant uo = 4x×10¯7 T · m/A is the permeability of free space. 7. Magnetic field produced by a current-carrying circular loop. There is a simple formula for the magnetic field strength at the center of a circular loop. It is B =, where R is the radius of the loop. One 2πr' Нol 2R way to get a larger field is to have N loops; then, the field is B = N Ho!. 2R Holil2 , here two parallel currents I1 and I2, 8. Magnetic force between two parallel conductors %3D 2nr separated by a distance r, l is length of the conductors.

A 1 XXX XX X X X X X XXXXX F=2x104 Downward b= 8MC force * find magnitude and direction of the speed of charge "mignatic feild Pointing to the right* B=2x10" T L=1m 2 *Acharge in a mignatic feild going into the page. *4 B = 2x10-³+ V=? Cuine Current I= 2s find the Direction of the force 3 magnitudo acting on this wire goiry Down

A heart defibrillator used by emergency medical sta to restart an accident victim’s heart has a power supply that produces an average 5000V over a short period of time. A defibrillator is basically a capacitor that discharges its stored charge in such a way that the charge moves through the human body, across the heart, as a current. If this capacitor is created from charging up plates 5cm on each side, with plastic insulator spacing of 3cm between the plates, then how much charge did the plates transfer to the human body?

If the voltage is 100 volts, what is the current through R2?

Opening of voltage-gated channels is driven by an intramembrane electric field acting on charged voltage-sensor domains. These domains move across the membrane and generate gating (displacement) currents. When these currents are integrated over time, they produce the gating charge generated by a population of channels. What would be the gating charge passing through the external circuit when the flat array of charges moves across the distance a inside the membrane? The hydrophobic thickness of the membrane is d, the dielectric constant ɛ, the density of charges is O and the area of the membrane is A (provide an analytic solution). start end A A a d d

A myelinated axon conducts nerve impulses at a speed of 40 m/s. What is the signal speed if the thickness of the myelin sheath is halved but no other changes are made to the axon?