Ch 27 Direct Current Circuits

The terminal voltage of a battery equals the _______ if the internal resistance is zero.

emf

What is the formula for the total power output of a battery?

P = I ΔV = I ε

What is the formula of power in relation to internal and external resistors

P = I^2(R+r)

How can the percentage of power delivered to a device be maximized?

By keeping the internal resistance of the battery as low as possible.

In resistors connected in series, the currents are _______.

the same

What is the same and what is different for resistors connected in series

Currents are the same, potentials add

What is the same and what is different for resistors connected in parallel

Potentials are the same, currents add

For resistors in parallel, what is the relationship between resistance and current

The lower resistance will have higher currents

What are the two main Kirchhoff rules

Junction rule: at any junction the sum of the currents must equal zero

Loop rule: The sum of potential differences across all elements around any circuits loop must be zero

When a resistor is traversed in the direction of the current, the potential difference across the resistor is _______.

V = -IR

When a resistor is traversed in the direction opposite the current, the potential difference across the resistor is _______.

V = +IR

When a source of emf is traversed opposite the emf (positive to negative), the potential difference is _______.

\-emf

When a source of emf is traversed in the direction of the emf (negative to positive), the potential difference is _______.

\+emf

When does a capacitor stop charging

When it reaches its maximum charge (Q = Cε)

What is the current when the capacitor is fully charged

Zero

What happens to the potential difference across the capacitor as the plates are being charged

It increases

When is the charge of the capacitor zero

When the switch closes

What happens when the maximum charge is reached

The current in the circuit is zero

Consider an RC circuit and assume that the battery has no internal resistance. Just after the switch is closed, the current in the battery is

Just after the switch is closed, there is no charge on the capacitor.