tailieunhanh - SAT II Physics (SN) Episode 2 Part 3

Tham khảo tài liệu 'sat ii physics (sn) episode 2 part 3', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A particle with a positive charge of 3 C moves upward at a speed of 10 m s. It passes simultaneously through a magnetic field of T directed into the page and an electric field of 2 N C directed to the right. How is the motion of the particle affected Answering this question is a matter of calculating the force exerted by the magnetic field and the force exerted by the electric field and then adding them together. The force exerted by the magnetic field is Using the right-hand-rule we find that this force is directed to the left. The force exerted by the electric field is This force is directed to the right. In sum we have one force of 6 N pushing the particle to the left and one force of 6 N pushing the particle to the right. The net force on the particle is zero so it continues toward the top of the page with a constant velocity of 10 m s. Magnetic Force on Current-Carrying Wires Since an electric current is just a bunch of moving charges wires carrying current will be subject to a force when in a magnetic field. When dealing with a current in a wire we obviously can t use units of q and v. However qv can equally be expressed in terms of II where I is the current in a wire and l is the length in meters of the wire both qv and Il are expressed in units of C m s. So we can reformulate the equation for the magnitude of a magnetic force in order to apply it to a current-carrying wire In this formulation is the angle the wire makes with the magnetic field. We determine the direction of the force by using the right-hand rule between the direction of the current and that of the magnetic field. 251 EXAMPLE In the figure above a magnetic field of T is applied locally to one part of an electric circuit with a 5 resistor and a voltage of 30 V. The length of wire to which the magnetic field is applied is 2 m. What is the magnetic force acting on that stretch of wire We are only interested in the stretch of wire on the right where the current flows in a downward direction.