Q: A 100 $$ m \Omega$$ resistor has a current of 2 A flowing through it. What is the power dissipated by the resistor?

$$P = I^2$ R = (2)^2$ \times 100 = 400 W$$

Question 1

A capacitor with initial charge $$Q is $$connected in series with a resistor $$R at$$ $$t=0. $$What is the expression for the charge $$q(t) on $$the capacitor at time $$t$$ during discharge?

Accepted Answer

$$q(t) = Q e$$^{-t/RC}$$

Question 2

In the circuit shown in the first image, what is the potential difference $$V_{ab}$$ across the blue box if the current $$i$$ flows from $$a to$$ $$b$$ and the box contains a resistor $$R$$?

Accepted Answer

$$V_{ab} = iR$$

Question 3

Which of the following statements about breaking a bar magnet (as shown in the second image) is correct?

Accepted Answer

Each piece becomes a smaller magnet with both a north and south pole.

Question 4

Which of the following best describes the pattern of iron filings around a bar magnet, as shown in the third image?

Accepted Answer

The filings align along the magnetic field lines, showing the direction and strength of the field.

Question 5

Which diagram in the fifth image correctly shows the magnetic field lines of a bar magnet?

Accepted Answer

Diagram 3

Question 6

A 100 $$m \Omega$$ resistor has a current of 2 A flowing through it. What is the power dissipated by the resistor?

Accepted Answer

$$P = I^2$ R = (2)^2$ 	imes 100 = 400 W$$

Question 7

Which of the following is true about the interaction between a bar magnet and a piece of iron, as shown in the sixth image?

Accepted Answer

The iron is attracted to both the north and south poles of the magnet.

Question 8

Which of the following best describes the Earth's magnetic field, as shown in the seventh image?

Accepted Answer

The Earth's geographic north pole is near the magnetic south pole.

Question 9

A charge $$q$$ moves with velocity $$\vec{v}$$ perpendicular to a magnetic field $$\vec{B}. $$What is the magnitude of the magnetic force on the charge?

Accepted Answer

$$F = qvB$$

Question 10

Which of the following is a correct statement about the direction of the magnetic force on a moving charge, as shown in the last image?

Accepted Answer

The force is perpendicular to both the velocity and the magnetic field.

Question 11

If a current of 0.1 A passes through the human body for 1 second, what is the likely effect?

Accepted Answer

It can be fatal.

Question 12

Which of the following is NOT a property of magnetic field lines?

Accepted Answer

They start and end at magnetic monopoles.

Question 13

A resistor $$R_1 is in $$series with a resistor $$R_2. $$What is the total resistance $$R_{eq}$$?

Accepted Answer

$$R_{eq} = R_1$ + R_2$

Question 14

A charge $$q$$ moves at an angle $$	heta to a $$magnetic field $$B. $$What is the magnitude of the force on the charge?

Accepted Answer

$$F = qvB \sin 	heta$$

Question 15

Which of the following is true about ammeters and voltmeters in a circuit?

Accepted Answer

Ammeters are connected in series and voltmeters in parallel.

Question 16

If a charged particle moves parallel to a magnetic field, what is the magnetic force on it?

Accepted Answer

Zero

Question 17

Which of the following is a correct application of Kirchhoff’s loop law?

Accepted Answer

The sum of the potential differences around any closed loop is zero.

Question 18

Which of the following is NOT a correct formula for power in an electric circuit?

Accepted Answer

$$P = IR^2$

Question 19

Which of the following best explains why magnetic field lines never start or stop at a point?

Accepted Answer

There are no magnetic monopoles; field lines always form closed loops.

Question 20

A circuit contains two resistors, $$R_1 = 100$$ \ \Omega$$ and R_2$ = 200 \ \Omega$$, in parallel. What is the equivalent resistance?

Accepted Answer

$$R_{eq} = \frac{R_1$ R_2$}{R_1$ + R_2$} = \frac{100 	imes 200}{100 + 200} = 66.7 \ \Omega$$

Week 5 Lec. 3

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