Physics Exam 2: Circuits, Ohm’s Law, Kirchhoff’s Rules & RC Time Constants

What is Ohm's Law?

Ohm's Law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R). It can be expressed as V = IR.

What is the SI unit for current?

The SI unit for current is the ampere (A).

What is the SI unit for resistance?

The SI unit for resistance is the ohm (Ω).

What is the SI unit for power?

The SI unit for power is the watt (W).

What happens to the current in resistors connected in series?

The current through each resistor in series is the same.

What happens to the voltage in resistors connected in parallel?

The voltage across each resistor in parallel is the same.

What happens to the voltage in capacitors connected in parallel?

The voltage across each capacitor in parallel is the same.

What happens to the charge in capacitors connected in series?

The charge on each plate of capacitors in series is the same.

What does Kirchhoff's First Rule state?

Kirchhoff's First Rule (Junction Rule) states that at any junction point, the sum of all currents entering the junction must equal the sum of all currents leaving the junction.

What does Kirchhoff's Second Rule state?

Kirchhoff's Second Rule (Loop Rule) states that the sum of the changes in potential around any closed path of a circuit must be zero.

How is the sign for resistance voltage determined?

The sign for resistance voltage is determined by your movement around a closed loop: it is negative if you move in the same direction as the current arrow and positive if you move in the opposite direction.

How is the sign for battery voltage determined?

The sign for battery voltage is determined by which battery line you move through last: it is positive if you cross the positive battery line last and negative if you cross the negative line last.

What is the effect of a current of 1 mA?

A current of 1 mA can be felt.

What is the effect of a current above 10 mA?

A current above 10 mA can cause muscle contraction.

What is the effect of a current between 80 to 100 mA?

A current between 80 to 100 mA can be fatal.

What is the resistance of dry skin?

The resistance of dry skin is approximately 1,000,000 ohms (106 Ω).

What is the resistance of wet skin?

The resistance of wet skin is approximately 1,000 ohms (103 Ω).

What is the formula for power in terms of current and resistance?

The formula for power is P = I²R.

What is the formula for voltage in terms of current and resistance?

The formula for voltage is V = IR.

How do you calculate the cost of electricity?

The cost of electricity can be calculated using the formula: Cost = Rate Power Time.

What is the terminal voltage of a battery?

The terminal voltage of a battery is the voltage output when the battery is connected to a load.

What is equivalent resistance?

Equivalent resistance is the total resistance of a circuit or a combination of resistors.

What is the RC time constant?

The RC time constant is the time it takes for the voltage across a capacitor to charge to about 63.2% of its maximum value when charging through a resistor.