awoda E) 0.014 A 9) Motional emf: A conducting bar slides without friction on two parallel horizontal rails that 50 cm apart and connected by a wire at one end. The resistance of the bar and the rails is constant and equal to 0.10 2. A uniform magnetic field is perpendicular to the plane of the rails. A 0.080-N force parallel to the rails is required to keep the bar moving at a constant speed of 0.50 m/s. What is the magnitude of the magnetic field? A) 0.10 T B) 0.25 T 9 gim 088 (A flows C) 0.36 T D) 0.54 T E) 0.93 T ent of t ideal solenoid having a circular cross-section, the

Using an electromagnetic flowmeter (Fig. P19.69), a heart surgeon monitors the flow rate of blood through an artery. Electrodes A and B make contact with the outer surface of the blood vessel, which has interior diameter 3.00 mm. (a) For a magnetic field magnitude of 0.040 0 T, a potential difference of 160 V appears between the electrodes. Calculate the speed of the blood. (b) Verify that electrode A is positive, as shown. Does the sign of the emf depend on whether the mobile ions in the blood are predominantly positively or negatively charged? Explain. Figure P19.69

A metal bar of length 25 cm is placed perpendicular to a uniform magnetic field of strength 3 T. (a) Determine the induced emf between the ends of the rod when it is not moving, (b) Determine the emf when the rod is moving perpendicular to its Length and magnetic field with a speed of 50 cm/s.

A metal bar of mass 500 g slides outward at a constant speed of 1.5 cm/s over two parallel rails separated by a distance of 30 cm which are pail of a U-shaped conductor. There is a uniform magnetic field of magnitude 2 T pointing out of the page over the entire area. The railing and metal bar have an equivalent resistance of 150 . (a) Determine the induced current, both magnitude and direction, (b) Find the direction of tire induced current if the magnetic field is pointing into the page, (c) Find the direction of the induced current if the magnetic field is pointed into the page and the bar moves inwards.

The magnetic field perpendicular to a single sire loop of diameter 10.0 cm decreases fron 0.50 T to zero. The re Is made of copper and has a diameter of 2.0 mm and length 1.0 cm. How much charge moves thrnugh the re while tt field is changing?

Is Ampere’s law valid for all closed paths? Why isn’t it normally useful for calculating a magnetic field?

Ail electron is moving at a speed of 1.0 104 in/s in a circular path of radius 2.0 cm inside a solenoid. The magnetic field of the solenoid is perpendicular to the plane of the electrons path. Find (a) the strength of the magnetic field inside the solenoid and (b) the current in the solenoid if it has 25 turns per centimeter.

Design a current loop that, when rotated in a uniform magnetic field of strength 0.10 T, will produce an emf =0 sin t. where 0=110V and 0=110V .

In Figure P20.65 the rolling axle of length 1.50 m is pushed along horizontal rails at a constant speed v = 3.00 m/s. A resist or R = 0.400 is connected to the rails at points a and b, directly opposite each other. (The wheels make good electrical contact with the rails, so the axle, rails, and R form a closed-loop circuit. The only significant resistance in the circuit is R.) A uniform magnetic field B = 0.800 T is directed vertically downward. (a) Find the induced current I in the resistor. (b) What horizontal force F is required to keep the axle rolling at constant speed? (c) Which end of the resistor, a or b. is at the higher electric potential? (d) Alter the axle rolls past the resistor, does the current in R reverse direction? Explain your answer. Figure P20.65

Sketch a plot of the magnitude of the magnetic field as a function of position r for a coax (Fig. P31.27).