# Homework Help: Check answers on a review sheet

1. Mar 1, 2004

### nautica

thanks

1) In a purely inductive circut, the current lags voltage by?

1/4 cycle

2) Which has the greatest effect in decreasing oscillation frequency of an LC circuit? Using Instead:
a) L/2 and C/2
b) L/2 and 2C
c) 2L and C/2
d) 2L and 2C I picked d

4) A coil has a resistance of 60 ohms and an impedance of 100 ohms. its reactance in ohms is: 80 Ohms

5) At any point the magnetic field lines are in the direction of:
a) the magnetic force on a moving poistive charge
b) the magnetic force on a moving negative charge
c) the velocity of a moving positive charge
d) the velocity of a moving negative charge
e) None of the above - I picked e)

6) and electron is moving north in a region where the magnetic field is south. the magnetic force exerted on the electron is? Zero

8) You push a permanent magnet with its north pole away from you toward a loop of conducting wire in front of you. Before the north pole enters the loop the current in the loop is?? zero

9) The normal to a certain 1 meter squared area makes an angle of 60 with a uniform mag field. the mag flux through this area is the same as the flux through a second area that is perpendicular to the field if the second area is???? .5 meters squared.

10) A magnetic field exerts a force on a charged particle:
a) always
b) never
c) if the particle is moving across the field lines (I picked c)
d) if the particle is moving with the field lines
e) if the particle is at rest

2. Mar 1, 2004

### Staff: Mentor

All look good except for #8.

3. Mar 1, 2004

### nautica

Re: Re: Check answers on a review sheet

I thought it was zero before it entered and then it resisted the change??

Nautica

4. Mar 1, 2004

### Staff: Mentor

Re: Re: Re: Check answers on a review sheet

No, the field extends beyond the pole of the magnet. As the field through the loop changes, a current is induced.

5. Mar 1, 2004

### nautica

So the current would be clockwise?

Last edited by a moderator: Mar 1, 2004